Commodore 64

The Commodore 64, also known as the C64, is an 8-bithome computer introduced in January 1982 by Commodore International (first shown at the Consumer Electronics Show, January 7–10, 1982, in Las Vegas).^[4] It has been listed in the Guinness World Records as the best-selling desktop computer model of all time,^[5] with independent estimates placing the number sold between 12.5 and 17 million units.^[2] Volume production started in early 1982, marketing in August for US$595 (equivalent to $1,990 in 2025).^[6] Preceded by the VIC-20 and Commodore PET, the C64 took its name from its 64 kibibytes(65,536 bytes) of RAM. With support for multicolor sprites and a custom chip for waveform generation, the C64 could create superior visuals and audio compared to systems without such custom hardware.^[7]

The C64 dominated the low-end computer market (except in the UK, France and Japan, lasting only about six months in Japan^[8]) for most of the later years of the 1980s.^[9] For a substantial period (1983–1986), the C64 had between 30% and 40% share of the US market and two million units sold per year,^[10] outselling IBM PC compatibles, the Apple II, and Atari 8-bit computers. Sam Tramiel, a later Atari president and the son of Commodore's founder, said in a 1989 interview, "When I was at Commodore we were building 400,000 C64s a month for a couple of years."^[11] In the UK market, the C64 faced competition from the BBC Micro, the ZX Spectrum, and later the Amstrad CPC 464,^[12] but the C64 was still the second-most-popular computer in the UK after the ZX Spectrum.^[13] The Commodore 64 failed to make any impact in Japan, as their market was dominated by Japanese computers, such as the NEC PC-8801, Sharp X1, Fujitsu FM-7 and MSX,^[14] and in France, where the ZX Spectrum, Thomson MO5 and TO7, and Amstrad CPC 464 dominated the market.^[15]

Parte del éxito del Commodore 64 se debió a su venta en tiendas minoristas convencionales en lugar de solo en tiendas especializadas en electrónica o informática. Commodore fabricaba muchas de sus piezas internamente para controlar los costos , incluyendo chips de circuitos integrados personalizados de MOS Technology . En Estados Unidos, se le ha comparado con el automóvil Ford Modelo T por su papel en llevar una nueva tecnología a los hogares de clase media a través de una producción en masa creativa y asequible. ^{[ 16 ]} Se han creado aproximadamente 10 000 títulos de software comercial para el Commodore 64, incluyendo herramientas de desarrollo, aplicaciones de productividad de oficina y videojuegos . ^{[ 17 ]} Los emuladores de C64 permiten que cualquier persona con una computadora moderna o una consola de videojuegos compatible ejecute estos programas hoy en día. Al C64 también se le atribuye la popularización de la demoscene informática y todavía lo utilizan algunos aficionados a la informática . ^{[ 18 ]} En 2011, 17 años después de su retirada del mercado, una investigación mostró que el reconocimiento de marca para el modelo aún era del 87 %. ^{[ 19 ]}

En enero de 1981, MOS Technology, Inc., la filial de diseño de circuitos integrados de Commodore , inició un proyecto para diseñar los chips gráficos y de audio para una consola de videojuegos de próxima generación . El trabajo de diseño para los chips, llamados MOS Technology VIC-II (Video Integrated Circuit para gráficos) y MOS Technology SID (Sound Interface Device para audio), se completó en noviembre de 1981. ^{[ 6 ]} Luego, Commodore comenzó un proyecto de consola de juegos que usaría los nuevos chips, llamada Ultimax o MAX Machine , diseñada por Yash Terakura de Commodore Japón. Este proyecto finalmente se canceló después de que solo se fabricaron unas pocas máquinas para el mercado japonés. ^{[ 20 ]} Al mismo tiempo, Robert "Bob" Russell (programador de sistemas y arquitecto en el VIC-20 ) y Robert "Bob" Yannes (ingeniero del SID) criticaron la línea de productos actual de Commodore, que era una continuación de la línea Commodore PET dirigida a usuarios comerciales. Con el apoyo de Al Charpentier (ingeniero del VIC-II) y Charles Winterble (gerente de MOS Technology), propusieron al director ejecutivo de Commodore, Jack Tramiel, una secuela de bajo costo del VIC-20. Tramiel dictó que la máquina debía tener 64 KB de memoria de acceso aleatorio (RAM). Aunque los chips de memoria de acceso aleatorio dinámico (DRAM) de 64 Kbit costaban más de US$100 (equivalente a US$299.35 en 2025) en ese momento, sabía que los precios de la DRAM de 64K estaban bajando y caerían a un nivel aceptable antes de que se alcanzara la producción en masa. El equipo pudo diseñar rápidamente la computadora porque, a diferencia de la mayoría de las demás compañías de computadoras domésticas, Commodore tenía su propia fábrica de semiconductores para producir chips de prueba; como la fábrica no estaba funcionando a plena capacidad, los costos de desarrollo formaban parte de los gastos generales corporativos existentes. Los chips estuvieron listos en noviembre, momento en el que Charpentier, Winterble y Tramiel decidieron seguir adelante con la nueva computadora; Este último fijó como fecha límite final el primer fin de semana de enero, para que coincidiera con la Feria de Electrónica de Consumo (CES) de 1982. ^{[ 6 ]}

The product was code named the VIC-40 as the successor to the popular VIC-20. The team that constructed it consisted of Yash Terakura,^[21]Shiraz Shivji,^[22] Bob Russell, Bob Yannes, and David A. Ziembicki. The design, prototypes, and some sample software were finished in time for the show, after the team had worked tirelessly over both Thanksgiving and Christmas weekends. The machine used the same case, same-sized motherboard, and same Commodore BASIC 2.0 in ROM as the VIC-20. BASIC also served as the user interfaceshell and was available immediately on startup at the READY prompt. When the product was to be presented, the VIC-40 product was renamed C64. The C64 made an impressive debut at the January 1982 Consumer Electronics Show, as recalled by Production Engineer David A. Ziembicki: "All we saw at our booth were Atari people with their mouths dropping open, saying, 'How can you do that for $595?'"^[6][23] The answer was vertical integration; due to Commodore's ownership of MOS Technology's semiconductor fabrication facilities, each C64 had an estimated production cost of US$135 (equivalent to $350 in 2022).^[6]

En julio de 1983, la revista BYTE afirmó que "el 64 se vende por 595 dólares . A ese precio, promete ser uno de los competidores más atractivos en el mercado de ordenadores personales de menos de 1000 dólares ". Describió el SID como "un verdadero sintetizador musical... la calidad del sonido hay que escucharla para creerla", al tiempo que criticaba el uso de Commodore BASIC 2.0, el rendimiento del disquete, que era "incluso más lento que la unidad del Atari 810 ", y el control de calidad de Commodore. BYTE ofreció más detalles, diciendo que el C64 tenía un "Commodore BASIC 2.0 inadecuado. Un BASIC interpretado de 8 KB", lo que asumieron que se debía a que "obviamente, Commodore piensa que la mayoría de los usuarios domésticos usarán software preinstalado; no hay ninguna disposición para usar gráficos (o sonido, como se mencionó anteriormente) dentro de un programa BASIC excepto mediante comandos POKE". Esta fue una de las pocas advertencias sobre el BASIC del C64 publicadas en revistas de informática. ^{[ 24 ]} Creative Computing afirmó en diciembre de 1984 que la C64 era "la ganadora indiscutible" en la categoría de computadoras domésticas de menos de $500 . A pesar de criticar su "unidad de disco lenta, solo dos teclas direccionales de cursor, nulo soporte del fabricante, interfaces no estándar, etc.", la revista afirmó que al precio de la C64, inferior a $500 , "no se puede conseguir otro sistema con las mismas características: 64K, color, gráficos sprite y gran cantidad de software disponible". La Tandy Color Computer quedó en segundo lugar. La Apple II fue la ganadora en la categoría de computadoras domésticas de más de $500 , categoría en la que se encontraba la Commodore 64 cuando se lanzó por primera vez a un precio de $595 . ^{[ 25 ]}

Commodore tenía fama de anunciar productos que nunca llegaban a salir al mercado , por lo que la compañía buscó lanzar el C64 rápidamente. La producción comenzó en la primavera de 1982 y los envíos en masa comenzaron en agosto. ^{[ 6 ]} El C64 se enfrentó a una amplia gama de ordenadores domésticos de la competencia , ^{[ 26 ]} pero, con un precio más bajo y un hardware más flexible, rápidamente superó en ventas a muchos de sus competidores.

In the United States, the greatest competitors were the Atari 8-bit computers, the Apple II, and the TI-99/4A. The Atari 400 and 800 had been designed to accommodate previously stringent FCC emissions requirements and so were expensive to manufacture. Though similar in specifications, the C64 and Apple II represented differing design philosophies; as an open architecture system, upgrade capability for the Apple II was granted by internal expansion slots, whereas the C64's comparatively closed architecture had only a single external ROM cartridge port for bus expansion. However, the Apple II used its expansion slots for interfacing with common peripherals like disk drives, printers, and modems; the C64 had a variety of ports integrated into its motherboard, which were used for these purposes, usually leaving the cartridge port free. Commodore's was not a completely closed system, however; the company had published detailed specifications for most of their models since the Commodore PET and VIC-20 days, and the C64 was no exception. This was in contrast to the TI-99/4A, as Texas Instruments focused less on hobbyists and more towards unsophisticated users.^[27] C64 sales were relatively slow due to a lack of software, reliability issues with early production models, particularly high failure rates of the PLA chip, which used a new production process, and a shortage of 1541 disk drives, which also suffered rather severe reliability issues. During 1983, however, a trickle of software turned into a flood and sales began rapidly climbing.

Commodore sold the C64 not only through its network of authorized dealers but also through department stores, discount stores, toy stores and college bookstores. The C64 had a built-in RF modulator and thus could be plugged into any television set. This allowed it (like its predecessor, the VIC-20) to compete directly against video game consoles such as the Atari 2600. Like the Apple IIe, the C64 could also output a composite video signal, avoiding the RF modulator altogether. This allowed the C64 to be plugged into a specialized monitor for a sharper picture. Unlike the IIe, the C64's NTSC output capability also included separate luminance/chroma signal output equivalent to (and electrically compatible with) S-Video, for connection to the Commodore 1702 monitor, providing even better video quality than a composite signal.

Aggressive pricing of the C64 is considered to have been a major catalyst in the video game crash of 1983. In January 1983, Commodore offered a $100 rebate in the United States on the purchase of a C64 to anyone that traded in another video game console or computer.^[28] To take advantage of this rebate, some mail-order dealers and retailers offered a Timex Sinclair 1000 (TS1000) for as little as $10 with the purchase of a C64. This deal meant that the consumer could send the TS1000 to Commodore, collect the rebate, and pocket the difference; Timex Corporation departed the computer market within a year. Commodore's tactics soon led to a price war with the major home computer manufacturers. The success of the VIC-20 and C64 contributed significantly to Texas Instruments and other smaller competitors exiting the field.

The price war with Texas Instruments was seen as a personal battle for Commodore president Jack Tramiel.^[29] Commodore dropped the C64's list price by $200 within two months of its release.^[6] In June 1983 the company lowered the price to $300 (equivalent to $1000 in 2025), and some stores sold the computer for $199. At one point, the company was selling as many C64s as all computers sold by the rest of the industry combined. Meanwhile, TI lost money by selling the TI-99/4A for $99.^[30] TI's subsequent demise in the home computer industry in October 1983 was seen as revenge for TI's tactics in the electronic calculator market in the mid-1970s, when Commodore was almost bankrupted by TI.^[31]

All four machines had similar memory configurations which were standard in 1982–83: 48 KB for the Apple II+^[32] (upgraded within months of C64's release to 64 KB with the Apple IIe) and 48 KB para el Atari 800. ^{[ 33 ]} Con un precio superior a $1200 , ^{[ 34 ]} el Apple II era aproximadamente el doble de caro, mientras que el Atari 800 costaba $899. Una clave del éxito del C64 fueron las agresivas tácticas de marketing de Commodore, y rápidamente explotaron las divisiones relativas de precio/rendimiento entre sus competidores con una serie de comerciales de televisión después del lanzamiento del C64 a finales de 1982. ^{[ 35 ]} La compañía también publicó documentación detallada para ayudar a los desarrolladores, ^{[ 36 ]} mientras que Atari inicialmente mantuvo la información técnica en secreto. ^{[ 37 ]}

Aunque muchos de los primeros juegos de C64 eran inferiores adaptaciones de juegos de Atari de 8 bits , a finales de 1983, la creciente base instalada hizo que los desarrolladores crearan nuevo software con mejores gráficos y sonido. ^{[ 38 ]} A finales de 1983 se extendieron rumores de que Commodore descontinuaría el C64, ^{[ 39 ]} pero era el único ordenador doméstico que no se había descontinuado y que estaba ampliamente disponible en los EE. UU. para entonces, con más de 500 000 vendidos durante la temporada navideña; ^{[ 40 ]} debido a problemas de producción en la cadena de suministro de Atari, a principios de 1984 "el Commodore 64 tiene prácticamente el mercado [de gama baja] para sí mismo en este momento", informó The Washington Post . ^{[ 41 ]}

Algunos de los modos gráficos de la 64 son realmente extraños y no tienen equivalente en Atari o Apple, como la posibilidad de cambiar el color de la base de los caracteres en toda la pantalla. Eso nos brindó una gran capacidad de color que no se había aprovechado.

Con las ventas en auge y los problemas iniciales de fiabilidad del hardware solucionados, el software para la C64 comenzó a crecer en tamaño y ambición durante 1984. Este crecimiento se convirtió en el principal objetivo de la mayoría de los desarrolladores de juegos estadounidenses. Las dos excepciones fueron Sierra , que en gran medida ignoró la C64 en favor de máquinas compatibles con Apple y PC, y Broderbund , que invirtió fuertemente en software educativo y desarrolló principalmente para la Apple II. En el mercado norteamericano, el formato de disco se había vuelto casi universal, mientras que el software basado en casete y cartucho prácticamente desapareció. La mayoría de los juegos desarrollados en EE. UU. para entonces eran lo suficientemente grandes como para requerir la carga múltiple desde el disco.

At a mid-1984 conference of game developers and experts at Origins Game Fair, Dan Bunten, Sid Meier, and a representative of Avalon Hill said that they were developing games for the C64 first as the most promising market.^[42] By 1985, games were an estimated 60 to 70% of Commodore 64 software.^[43]Computer Gaming World stated in January 1985 that companies such as Epyx that survived the video game crash did so because they "jumped on the Commodore bandwagon early".^[44] Over 35% of SSI's 1986 sales were for the C64, ten points higher than for the Apple II. The C64 was even more important for other companies,^[45] which often found that more than half the sales for a title ported to six platforms came from the C64 version.^[46] That year, Computer Gaming World published a survey of ten game publishers that found that they planned to release forty-three Commodore 64 games that year, compared to nineteen for Atari and forty-eight for Apple II,^[47] and Alan Miller stated that Accolade developed first for the C64 because "it will sell the most on that system".^[48]

In Europe, the primary competitors to the C64 were British-built computers: the Sinclair ZX Spectrum, the BBC Micro, and the Amstrad CPC 464. In the UK, the 48K Spectrum had not only been released a few months ahead of the C64's early 1983 debut, but it was also selling for £175, less than half the C64's £399 price. The Spectrum quickly became the market leader and Commodore had an uphill struggle against it in the marketplace. The C64 did however go on to rival the Spectrum in popularity in the latter half of the 1980s. Adjusted to the population size, the popularity of Commodore 64 was the highest in Finland at roughly 3 units per 100 inhabitants,^[49] where it was subsequently marketed as "the Computer of the Republic".^[50]

By early 1985 the C64's price was $149; with an estimated production cost of $35–50, its profitability was still within the industry-standard markup of two to three times.^[6] Commodore sold about one million C64s in 1985 and a total of 3.5 million by mid-1986. Although the company reportedly attempted to discontinue the C64 more than once in favor of more expensive computers such as the Commodore 128, demand remained strong.^[51][52] In 1986, Commodore introduced the 64C,^[53] a redesigned 64, which Compute! saw as evidence that—contrary to C64 owners' fears that the company would abandon them in favor of the Amiga and 128—"the 64 refuses to die".^[54] Its introduction also meant that Commodore raised the price of the C64 for the first time, which the magazine cited as the end of the home-computer price war.^[55] Software sales also remained strong; MicroProse, for example, in 1987 cited the Commodore and IBM PC markets as its top priorities.^[56]

By 1988, PC compatibles were the largest and fastest-growing home and entertainment software markets, displacing former leader Commodore.^[57] Software sales for Apple II and Atari 8-bit decreased, but sales for the 64 remained strong,^[58] albeit almost unchanged in the third quarter of 1988 year over year, while the overall market grew 42% driven by PC games.^[59] Commodore was still selling 1 to 1.5 million 64 units worldwide each year of what Computer Chronicles that year called "the Model T of personal computers".^[60] Epyx CEO Dave Morse cautioned that "there are no new 64 buyers, or very few. It's a consistent group that's not growing... it's going to shrink as part of our business."^[61] One computer gaming executive stated that the Nintendo Entertainment System's enormous popularity – seven million sold in 1988, almost as many as the number of C64s sold in its first five years – had stopped the C64's growth. Trip Hawkins reinforced that sentiment, stating that Nintendo was "the last hurrah of the 8-bit world".^[62]

SSI abandonó el mercado de Commodore 64 en 1991, después de la mayoría de sus competidores. ^{[ 63 ]} Ultima VI , lanzado en 1991, fue el último lanzamiento importante de un juego para C64 de un desarrollador norteamericano, y Los Simpson , publicado por Ultra Games , fue la última conversión de arcade. Este último fue un ejemplo poco común de una adaptación de arcade desarrollada en EE. UU., ya que después de los primeros años del C64, la mayoría de las conversiones de arcade fueron producidas por desarrolladores británicos y convertidas a formato NTSC y de disco para el mercado estadounidense; los desarrolladores estadounidenses, en cambio, se centraron en géneros de juegos más orientados a la computadora, como los RPG y las simulaciones. En el mercado europeo, el software en disco era más raro y los casetes eran el método de distribución más común; esto llevó a una mayor prevalencia de títulos de arcade y juegos más pequeños y de menor presupuesto que podían caber completamente en la memoria de la computadora sin necesidad de multicarga. Los programadores europeos también tendieron a explotar las características avanzadas del hardware del C64 más que sus homólogos estadounidenses. ^{[ 64 ]}

El paquete Commodore 64 Light Fantastic se lanzó a tiempo para la temporada navideña de 1989. El paquete incluía una C64C, una pistola de luz Cheetah Defender 64 y gafas 3D. Este paquete incluía varios juegos compatibles con la pistola de luz, incluyendo algunos desarrollados exclusivamente para su lanzamiento (Mindscape).

En Estados Unidos, la demanda de ordenadores de 8 bits prácticamente cesó al comenzar la década de 1990, cuando los PC compatibles dominaron por completo el mercado informático. Sin embargo, el C64 siguió siendo popular en el Reino Unido y otros países europeos. Su desaparición definitiva no se debió a la falta de demanda ni al coste del propio C64 (que seguía siendo rentable a un precio de venta al público de entre 44 y 50 libras), sino al coste de producción de la unidad de disquete. En marzo de 1994, en la feria CeBIT de Hannover , Alemania , Commodore anunció que el C64 se dejaría de fabricar definitivamente en 1995, señalando que el Commodore 1541 costaba más que el propio C64. ^{[ 65 ]}

Sin embargo, solo un mes después, en abril de 1994, la empresa se declaró en bancarrota . Cuando Commodore quebró, se interrumpió toda la producción de su inventario, incluido el C64, poniendo fin así a la vida útil del C64.+Producción de 1/2 año . Se han hecho afirmaciones de ventas de 17, 22 y 30 millones de unidades de C64 vendidas en todo el mundo. Sin embargo, los registros de ventas de la compañía indican que el número total fue de aproximadamente 12,5 millones. ^{[ 66 ]} Con base en esa cifra, el Commodore 64 siguió siendo la tercera plataforma informática más popular en el siglo XXI hasta 2017, cuando la familia Raspberry Pi lo reemplazó. ^{[ 67 ]}

While 360,000 C64s were sold in 1982, about 1.3 million were sold in 1983, followed by a large spike in 1984 when 2.6 million were sold. After that, sales held steady at between 1.3 and 1.6 million a year for the remainder of the decade and then dropped off after 1989. North American sales peaked between 1983 and 1985 and gradually tapered off afterward, while European sales remained quite strong into the early 1990s.^[2] Commodore itself reported a robust sales figure of over 800,000 units during the 1991 fiscal year, but sales during the 1993 fiscal year had declined to fewer than 200,000 units. Throughout the early 1990s, European sales had accounted for more than 80% of Commodore's total sales revenue.^[68]

On June 7, 2025, YouTuber Christian Simpson of the channel Retro Recipes (later renamed to Retro Recipes x Commodore) released the video titled "Can We Save The COMMODORE Brand? My Biggest Project Yet",^[69] at the end of which he hinted at acquiring the entire holding company maintaining the original Commodore trademarks and branding (Commodore Corporation B.V.). On June 28, 2025, a follow up video was released which announced that an agreement had been reached and hinted at an upcoming hardware release. On July 12, 2025, the newly revived magazine Compute!'s Gazette in its first edition announced the re-release of the original Commodore 64, which coincided with a video announcement from Retro Recipes x Commodore,^[70] The Commodore 64 Ultimate is an FPGA based re-implementation of the original C64 hardware which retains compatibility with existing C64 peripherals and cartridges while offering expanded capabilities and modern connectivity. The system was created with community partners and their projects such as Gideon Zweijtzer (of Gideon's Logic) and a customized variant of the Ultimate64 Elite-II mainboard. The base model re-release features a breadbin styled case and keyboard with classic coloring, while other editions offer RGB lighting and transparent / semi-transparent cases. The original schedule called for units to be shipped in October or November 2025. As of January 2026, the Commodore 64 Ultimate had been released to reviewers, with units due to ship in March 2026.^[71]

In 1982, Commodore released the MAX Machine in Japan. It was called the Ultimax in the United States and VC-10 in Germany. The MAX was intended to be a game console with limited computing capability and was based on a cut-down version of the hardware family later used in the C64. The MAX was discontinued months after its introduction because of poor sales in Japan.^[72]

1983 saw Commodore attempt to compete with the Apple II's hold on the US education market with the Educator 64,^[73] essentially a C64 and "green" monochrome monitor in a PET case. Schools preferred the all-in-one metal construction of the PET over the standard C64's separate components, which could be easily damaged, vandalized, or stolen.^[74] Schools did not prefer the Educator 64 to the wide range of software and hardware options the Apple IIe was able to offer, and it was produced in limited quantities.^[75]

Also in 1983, Commodore released the SX-64, a portable version of the C64. The SX-64 has the distinction of being the first commercial full-colorportable computer.^[76] While earlier computers using this form factor only incorporate monochrome ("green screen") displays, the base SX-64 unit features a 5 in (130 mm) color cathode ray tube (CRT) and one integrated 1541 floppy disk drive. Even though Commodore claimed in advertisements that it would have dual 1541 drives, when the SX-64 was released there was only one and the other became a floppy disk storage slot. Also, unlike most other C64s, the SX-64 does not have a datasette connector so an external cassette was not an option.^[77]

Two designers at Commodore, Fred Bowen and Bil Herd, were determined to rectify the problems of the Plus/4. They intended that the eventual successors to the C64—the Commodore 128 and 128D computers (1985)—were to build upon the C64, avoiding the Plus/4's flaws.^[78][79] The successors had many improvements such as a BASIC with graphics and sound commands (like almost all home computers not made by Commodore^[80][81][82]), 80-column display ability, and full CP/M compatibility. The decision to make the Commodore 128plug compatible with the C64 was made quietly by Bowen and Herd, software and hardware designers respectively, without the knowledge or approval by the management in the post Jack Tramiel era. The designers were careful not to reveal their decision until the project was too far along to be challenged or changed and still make the impending Consumer Electronics Show (CES) in Las Vegas.^[78] Upon learning that the C128 was designed to be compatible with the C64, Commodore's marketing department independently announced that the C128 would be 100% compatible with the C64, thereby raising the bar for C64 support. In a case of malicious compliance, the 128 design was altered to include a separate "64 mode" using a complete C64 environment to try to ensure total compatibility.^[83]

The C64's designers intended the computer to have a new, wedge-shaped case within a year of release, but the change did not occur.^[6] In 1986, Commodore released the 64C computer, which is functionally identical to the original, which was nicknamed the Breadbin 64 after the release of the 64C. The exterior design was remodeled in the sleeker style of the Commodore 128.^[52] The 64C uses new versions of the SID, VIC-II, and I/O chips being deployed. Models with the C64E board had the graphic symbols printed on the top of the keys, instead of the normal location on the front. The sound chip (SID) was changed to use the MOS 8580 chip, with the core voltage reduced from 12V to 9V. The most significant changes include different behavior in the filters and in the volume control, which result in some music/sound effects sounding differently than intended, and in digitally sampled audio being almost inaudible, respectively (though both of these can mostly be corrected-for in software). The 64 KiB RAM memory went from eight chips to two chips. BASIC and the KERNAL went from two separate chips into one 16 KiB ROM chip. The PLA chip and some TTL chips were integrated into a DIL 64-pin chip. The "252535-01" PLA integrated the color RAM as well into the same chip. The smaller physical space made it impossible to put in some internal expansions like a floppy-speeder.^[84] In the United States, the 64C was often bundled with the third-party GEOSgraphical user interface (GUI)-based operating system, as well as the software needed to access Quantum Link. The 1541 drive received a matching face-lift, resulting in the 1541C. Later, a smaller, sleeker 1541-II model was introduced, along with the 800 KB^[85] 3.5-inch microfloppy1581.

En 1990, el C64 se relanzó como consola de juegos, llamada C64 Games System (C64GS), con la mayoría de las opciones de conectividad externa eliminadas. ^{[ 86 ]} Se realizó una modificación simple a la placa base del 64C para permitir la inserción de cartuchos desde arriba. Una ROM modificada reemplazó el intérprete BASIC con una pantalla de arranque para informar al usuario que insertara un cartucho. Diseñado para competir con el Nintendo Entertainment System y el Master System de Sega , sufrió ventas muy bajas en comparación con sus rivales. Fue otro fracaso comercial para Commodore y nunca se lanzó fuera de Europa. El sistema de juegos Commodore carecía de teclado, por lo que no se podía usar ningún software que lo requiriera.

En 1990, se creó un prototipo del Commodore 65 (también conocido como "C64DX"), un sucesor avanzado del C64 , pero el proyecto fue cancelado por el presidente de Commodore, Irving Gould, en 1991. Las especificaciones del C65 eran impresionantes para un ordenador de 8 bits, con características comparables a las del Apple IIGS de 16 bits . Por ejemplo, podía mostrar 256 colores en la pantalla, mientras que los Amiga basados ​​en OCS solo podían mostrar 64 en modo HalfBrite (32 colores y transformaciones de brillo reducido). Aunque no se dio ninguna razón específica para la cancelación del C65, habría competido en el mercado con los Amiga de gama baja de Commodore y el Commodore CDTV .

En 1982, las capacidades gráficas y de sonido del C64 solo eran rivalizadas por las de los ordenadores Atari de 8 bits y parecían excepcionales en comparación con el popular Apple II . A menudo se le atribuye al C64 el inicio de la subcultura demoscene (véase Commodore 64 demos ). Todavía se utiliza activamente en la demoscene, ^{[ 87 ]} especialmente para la música (su chip de sonido SID incluso se utiliza en tarjetas de sonido especiales para PC y en el sintetizador Elektron SidStation ). Aunque otros ordenadores lo alcanzaron rápidamente, el C64 siguió siendo un fuerte competidor para las consolas de videojuegos posteriores Nintendo Entertainment System (NES) y Master System , gracias en parte a su base de software ya establecida.

Debido a los bajos ingresos y al dominio del ZX Spectrum en el Reino Unido, casi todo el software británico para C64 utilizaba cintas de casete. Pocos programas para C64 en casete se lanzaron en EE. UU. después de 1983 y, en Norteamérica, el disquete era el principal método de distribución de software. La ranura para cartuchos del C64 también fue una característica utilizada principalmente durante los dos primeros años del ordenador en el mercado estadounidense y quedó rápidamente obsoleta una vez que mejoraron el precio y la fiabilidad de las unidades 1541. Unos pocos juegos de la región PAL utilizaron cartuchos con conmutación de bancos para sortear el límite de memoria de 16 KiB.

Como era habitual en los ordenadores domésticos de principios de los años 80, el C64 incluía un intérprete BASIC en la ROM. El núcleo, las operaciones de entrada/salida y las unidades de cinta/disco se controlaban mediante comandos personalizados en lenguaje BASIC. La unidad de disco tenía su propio microprocesador de interfaz y rutinas de entrada/salida en la ROM (firmware), al igual que los sistemas CBM/PET anteriores y los Atari 400 y Atari 800. Esto significaba que no se dedicaba espacio de memoria a ejecutar un sistema operativo de disco , como ocurría con sistemas anteriores como el Apple II y el TRS-80 .

Se utilizó Commodore BASIC 2.0 en lugar del más avanzado BASIC 4.0 de la serie PET, ya que no se esperaba que los usuarios de C64 necesitaran las mejoras orientadas al disco de BASIC 4.0. La compañía no esperaba que muchos compraran una unidad de disco, y el uso de BASIC 2.0 simplificó la transición de los propietarios de VIC-20 al 64. ^{[ 88 ]} "La elección de BASIC 2.0 en lugar de 4.0 se hizo tras una profunda reflexión, no al azar. No se espera que el usuario típico de un C64 necesite los comandos directos del disco tanto como otras extensiones, y la cantidad de memoria que se asignaría a BASIC debía ser limitada. Optamos por dejar espacio de expansión para extensiones de color y sonido en lugar de las funciones del disco. Como resultado, tendrá que manejar el disco de la manera más engorrosa de los 'viejos tiempos'." ^{[ 89 ]}

La versión de Microsoft BASIC no es muy completa y no incluye comandos específicos para la manipulación de sonido o gráficos, sino que requiere que los usuarios utilicen los comandos " PEEK y POKE " para acceder directamente a los registros del chip de gráficos y sonido. Para proporcionar comandos extendidos, incluyendo gráficos y sonido, Commodore produjo dos extensiones diferentes basadas en cartuchos para BASIC 2.0: Simons' BASIC y Super Expander 64. Otros lenguajes disponibles para el C64 incluyen Pascal , C , ^{[ 90 ] [ 91 ]} Logo , Forth , ^{[ 92 ]} y FORTRAN . Se produjeron compiladores para BASIC 2.0 como Petspeed 2 (de Commodore), Blitz (de Jason Ranheim) y Turbo Lightning (de Ocean Software ). La mayoría del software comercial para C64 estaba escrito en lenguaje ensamblador, ya sea desarrollado en una computadora más grande o directamente en el C64 usando un monitor de código máquina o un ensamblador. Esto maximizaba la velocidad y minimizaba el uso de memoria. Algunos juegos, en particular los de aventuras, utilizaban lenguajes de scripting de alto nivel y, en ocasiones, mezclaban BASIC con lenguaje de máquina.

Se han desarrollado muchos sistemas operativos de terceros para la C64. Además del GEOS original , se han creado dos sistemas compatibles con GEOS: Wheels y GEOS megapatch. Ambos requieren actualizaciones de hardware en la C64 original. Existen o han existido otros sistemas operativos, como WiNGS OS, LUnix (similar a Unix y operado desde la línea de comandos) y el sistema operativo embebido Contiki , con interfaz gráfica completa. Otros sistemas operativos menos conocidos incluyen ACE, Asterix, DOS/65 y GeckOS . C64 OS, aunque no es un sistema operativo completo, está disponible comercialmente y continúa en desarrollo activo. Cuenta con una interfaz gráfica completa en modo de caracteres y muchas otras características modernas. Se lanzó una versión de CP/M , pero requiere la adición de un procesador Z80 externo al bus de expansión. Además, el procesador Z80 tiene una velocidad reducida para ser compatible con el bus de memoria de la C64, por lo que su rendimiento es inferior al de otras implementaciones de CP/M. Tanto el CP/M para C64 como para C128 adolecen de una escasez de software; si bien la mayoría del software comercial para CP/M puede ejecutarse en estos sistemas, los soportes de software son incompatibles entre plataformas. El bajo uso de CP/M en Commodore hizo que las compañías de software no vieran la necesidad de invertir en la creación de versiones para el formato de disco de Commodore. El cartucho de CP/M para C64 tampoco es compatible con nada excepto con las primeras placas base 326298. ^{[ 93 ]}

During the 1980s, the Commodore 64 was used to run bulletin board systems using software packages such as Punter BBS, Bizarre 64, Blue Board, C-Net, Color 64, CMBBS, C-Base, DMBBS, Image BBS, EBBS, and The Deadlock Deluxe BBS Construction Kit, often with sysop-made modifications. These boards sometimes were used to distribute cracked software. As late as December 2013, there were 25 such Bulletin Board Systems in operation, reachable via the Telnet protocol.^[94] There were major commercial online services, such as Compunet (UK), CompuServe (US – later bought by America Online), The Source (US), and Minitel (France) among many others. These services usually required custom software which was often bundled with a modem and included free online time as they were billed by the minute. Quantum Link (or Q-Link) was a US and Canadian online service for Commodore 64 and 128 personal computers that operated from November 5, 1985, to November 1, 1994. It was operated by Quantum Computer Services of Vienna, Virginia, which in October 1991 changed its name to America Online and continued to operate its AOL service for the IBM PC compatible and Apple Macintosh. Q-Link was a modified version of the PlayNET system, which Control Video Corporation (CVC, later renamed Quantum Computer Services) licensed.

The first graphical character-based interactive environment is Club Caribe. First released as Habitat in 1988, Club Caribe was introduced by LucasArts for Q-Link customers on their Commodore 64 computers. Users could interact with one another, chat and exchange items. Although the game's open world was very basic, its use of online avatars and the combination of chat and graphics was revolutionary. Online graphics in the late 1980s were severely restricted by the need to support modem data transfer rates as low as 300 bits per second. Habitat's graphics were stored locally on floppy disk, eliminating the need for network transfer.^[95]

The C64 uses an 8-bitMOS Technology 6510microprocessor that is almost identical to the 6502 but has three-state buses, a different pinout, slightly different clock signals and other minor changes for this application. It also has six I/O lines on otherwise-unused legs on the 40-pin IC package. These are used for two purposes in the C64: to bank-switch the machine's read-only memory (ROM) in and out of the processor's address space, and to operate the datasette tape recorder. The C64 has 64 KB of 8-bit-wide dynamic RAM, 1 KB of 4-bit-wide static color RAM for text mode, and 38 KB are available to built-in Commodore BASIC 2.0 on startup. There is 20 KB of ROM, made up of the BASIC interpreter, the KERNAL, and the character ROM. Because the processor can only address 64 KB at a time, the ROM was mapped into memory and only 38911 bytes of RAM (plus 4 KB between the ROMs) were available at startup. Most "breadbin" Commodore 64s used 4164 DRAM with eight chips totaling 64K of system RAM. Later models, featuring Assy 250466 and Assy 250469 motherboards, used 41464 DRAM (64K×4) chips which stored 32 KB per chip (so only two were required). Because 4164 DRAMs are 64K×1, eight chips are needed to make an entire byte; the computer will not function without all of them present. The first chip contains Bit 0 for the memory space, the second chip contains Bit 1, and so forth.

The C64 performs a RAM test on power-up and if a RAM error is detected, the amount of free BASIC memory will be lower than the normal 38,911. If the faulty chip is in lower memory, then an ?OUT OF MEMORY IN 0 error is displayed rather than the usual BASIC startup banner.

The C64 uses a complicated memory-banking scheme; the normal power-on default is the BASIC ROM mapped in at $A000–$BFFF, and the screen editor (KERNAL) ROM at $E000–$FFFF. RAM under the system ROMs can be written to, but not read back, without swapping out the ROMs. Memory location $01 contains a register with control bits for enabling or disabling the system ROMs and the I/O area at $D000. If the KERNAL ROM is swapped out, BASIC will be removed at the same time.^{[96]: 264 [97]} BASIC is not active without the KERNAL; BASIC often calls KERNAL routines, and part of the ROM code for BASIC is in the KERNAL ROM.

The character ROM is normally invisible to the CPU. The character ROM may be mapped into $D000–$DFFF, where it is then visible to the CPU. Because doing so necessitates swapping out the I/O registers, interrupts must first be disabled. By removing I/O from the memory map, $D000–$DFFF becomes free RAM.

C64 cartridges map into assigned ranges in the CPU's address space. The most common cartridge auto-starting requires a string at $8000 which contains "CBM80" followed by the address where program execution begins. A few C64 cartridges released in 1982 use Ultimax mode (or MAX mode), a leftover feature of the unsuccessful MAX Machine. These cartridges map into $F000 and displace the KERNAL ROM. If Ultimax mode is used, the programmer will have to provide code for handling system interrupts. The cartridge port has 16 address lines, which grants access to the computer's entire address space if needed. Disk and tape software normally load at the start of BASIC memory ($0801), and use a small BASIC stub (such as 10 SYS(2064)) to jump to the start of the program. Although no Commodore 8-bit machine except the C128 can automatically boot from a floppy disk, some software intentionally overwrites certain BASIC vectors in the process of loading so execution begins automatically (instead of requiring the user to type RUN at the BASIC prompt after loading).

About 300 cartridges were released for the C64, primarily during the machine's first 2+1⁄2 years on the market, after which most software outgrew the 16 KB cartridge limit. One notable third-party expansion was the Power Cartridge, developed by Dutch company Kolff Computer Supplies (KCS). It provided a BASIC extension toolkit, a machine code monitor, a reset button, and fastload routines that accelerated cassette and disk access (up to 10× and 6× respectively). Popular in the Benelux region, it was used for both productivity and programming purposes.^[98] Larger software companies, such as Ocean Software, began releasing games on bank-switched cartridges to overcome the 16 KB cartridge limit during the C64's final years.

Commodore did not include a reset button on its computers until the CBM-II line, but third-party cartridges had a reset button. A soft reset can be triggered by jumping to the CPU reset routine at $FCE2 (64738). A few programs use this as an exit feature, although it does not clear memory.

The KERNAL ROM underwent three revisions, mainly designed to fix bugs. The initial version is only found on 326298 motherboards (used in the first production models), and cannot detect whether an NTSC or PAL VIC-II is present. The second revision is found on all C64s made from late 1982 through 1985. The final KERNAL ROM revision was introduced on the 250466 motherboard (late breadbin models with 41464 RAM), and is found in all C64Cs. The 6510 CPU is clocked at 1.023 MHz (NTSC) and 0.985 MHz (PAL),^[99] lower than some competing systems; the Atari 800, for example, is clocked at 1.79 MHz). Performance can be boosted slightly by disabling the VIC-II's video output via a register write. This feature is often used by tape and disk fast loaders and the KERNAL cassette routine to keep a standard CPU cycle timing not modified by the VIC-II's sharing of the bus.

The restore key is gated directly to the CPU's NMI line, and will generate an NMI if pressed. The KERNAL handler for the NMI checks if run/stop is also pressed; if not, it ignores the NMI and exits. Run/stop-restore is normally a soft reset in BASIC which restores all I/O registers to their power-on default state, but does not clear memory or reset pointers; any BASIC programs in memory will be left untouched. Machine-language software usually disables run/stop-restore by remapping the NMI vector to a dummy RTI instruction. The NMI can also be used for an extra interrupt thread by programs, but risks a system lockup or other undesirable side effects if the restore key is accidentally pressed (which activates the NMI thread).

(from top) Commodore's version of the Atari joystick; a set of analog paddles; a 1350/1351 mouse, and DE-9 Atari-style joystick ports

The C64 retained the VIC-20's DE-9Atari joystick port and added another; any Atari-specification game controller can be used on a C64. The joysticks are read from the registers at $DC00 and $DC01, and most software is designed to use a joystick in port 2 for control rather than port 1; the upper bits of $DC00 are used by the keyboard, and an I/O conflict can result. Although it is possible to use Segagamepads on a C64, it is not recommended; their slightly different signal can damage the CIA chip. The SID chip's register $D419, used to control paddles, is an analog input. A handful of games, primarily released early in the computer's life cycle, can use paddles. In 1986, Commodore released two mice for the C64 and C128: the 1350 and 1351. The 1350 is a digital device read from the joystick registers, and can be used with any program supporting joystick input. The 1351 is an analog potentiometer-based mouse, read with the SID's analog-to-digital converter.

The VIC-II graphics chip features a new palette, eight hardware sprites per scanline (enabling up to 112 sprites per PAL screen), scrolling capabilities, and two bitmap graphics modes.

The standard text mode features 40 columns, like most Commodore PET models; the built-in character encoding is not standard ASCII but PETSCII, an extended form of ASCII-1963. The KERNAL ROM sets the VIC-II to a dark-blue background on power-up, with a light-blue border and text. Unlike the PET and VIC-20, the C64 uses double-width text; some early VIC-IIs had poor video quality which resulted in a fuzzy picture. Most screenshots show borders around the screen, a feature of the VIC-II chip. By utilizing interrupts to reset hardware registers with precise timing, it was possible to place graphics within the borders and use the full screen.^[100]

The C64 has a resolution of 320×200 pixels, consisting of a 40×25 grid of 8×8 character blocks. It has 256 predefined character blocks, known as PETSCII. The character set can be copied into RAM and modified by a programmer.

There are three color modes: high resolution, with two colors available per character block (one foreground and one background), multicolor (four colors per character block – three foreground and one background), and extended color (each individual character on the text screen may have one of four different background colors; the trade-off is that the character set is limited to the first 64 characters in the character set). In multicolor mode, attributes are shared between pixel pairs so the effective visible resolution is 160×200 pixels; only 16 KiB of memory is available for the VIC-II video processor.

Since the C64 has a bitmapped screen, it is possible (but slow) to draw each pixel individually. Most programmers used techniques developed for earlier, non-bitmapped systems like the Commodore PET and TRS-80. A programmer redraws the character set, and the video processor fills the screen block by block from the top left corner to the bottom right corner. Two types of animation are used: character block animation and hardware sprites.

The user draws a series of characters of a person walking, possibly two in the middle of the block and another two walking in and out of the block. Then the user sequences them so the character walks into the block and out again. Drawing a series of these gets a person walking across the screen. By timing the redraw to occur when the television screen blanks out to restart drawing the screen, there will be no flicker. For this to happen, a user programs the VIC-II that it generates a raster interrupt when video flyback occurs. This technique is used in the Space Invaders arcade game.

Horizontal and vertical pixel scrolling of up to one character block is supported by two hardware scroll registers. Depending on timing, hardware scrolling affects the entire screen or selected lines of character blocks. On a non-emulated C64, scrolling is glass-like and blur-free.

A sprite is a character which moves over an area of the screen, draws over the background, and redraws it after it moves. This differs from character block animation, where the user flips character blocks. On the C64, the VIC-II video controller handles most sprite emulation; the programmer defines the sprite and where it goes.

The C64 has two types of sprites, respecting their color-mode limitations. Hi-res sprites have one color (one background and one foreground), and multi-color sprites have three (one background and three foreground). Color modes can be split or windowed on a single screen. Sprites can be doubled in size vertically and horizontally up to four times their size, but the pixel attributes are the same – the pixels become "fatter". There are eight sprites, and all eight can be shown in each horizontal line concurrently. Sprites can move with glassy smoothness in front of, and behind, screen characters and other sprites.

The hardware sprites of a C64 can be displayed on a bitmapped (high-resolution) screen or a text-mode screen in conjunction with fast and smooth character block animation. Software-emulated sprites on systems without support for hardware sprites, such as the Apple II and ZX Spectrum, required a bitmapped screen. Sprite-sprite and sprite-background collisions are detected in hardware, and the VIC-II can be programmed to trigger an interrupt accordingly.

The SID chip has three channels, each with its own ADSR envelope generator and filter capabilities. Ring modulation makes use of channel three to work with the other two channels. Bob Yannes developed the SID chip and, later, co-founded the synthesizer company Ensoniq. Composers and programmers of game music on the C64 include Rob Hubbard, Jeroen Tel, Tim Follin, David Whittaker, Chris Hülsbeck, Ben Daglish, Martin Galway, Kjell Nordbø and David Dunn. Due to the chip's three channels, chords are often played as arpeggios. It was also possible to continuously update the master volume with sampled data to enable the playback of 4-bit digitized audio. By 2008, it was possible to play four-channel 8-bit audio samples and two SID channels and still use filtering.^[101]

There are two versions of the SID chip: the 6581 and the 8580. The MOS Technology 6581 was used in the original ("breadbin") C64s, the early versions of the 64C, and the Commodore 128. The 6581 was replaced with the MOS Technology 8580 in 1987. Although the 6581 sound quality is a little crisper, it lacks the 8580's versatility; the 8580 can mix all available waveforms on each channel, but the 6581 can only mix waveforms in a channel in a limited fashion. The main difference between the 6581 and the 8580 is the supply voltage; the 6581 requires 12 volts, and the 8580 9 volts. A modification can be made to use the 6581 in a newer 64C board (which uses the 9-volt chip).

In 1986, the Sound Expander was released for the Commodore 64. It was a sound module with a Yamaha YM3526 chip capable of FM synthesis, primarily intended for professional music production.^[102][103]

Commodore made many changes to the C64's hardware, sometimes introducing compatibility issues.^[104] The computer's rapid development and Commodore and Jack Tramiel's focus on cost-cutting instead of product testing resulted in several defects which caused developers like Epyx to complain and required many revisions; Charpentier said that "not coming a little close to quality" was one of the company's mistakes.^[6]

Cost reduction was the reason for most of the revisions. Reducing manufacturing costs was vitally important to Commodore's survival during the price war and lean years of the 16-bit era. The C64's original (NMOS-based) motherboard went through two major redesigns and a number of revisions, exchanging positions of the VIC-II, SID and PLA chips. Much of the cost was initially eliminated by reducing the number of discrete components, such as diodes and resistors, which enabled a smaller printed circuit board. There were 16 C64 motherboard revisions to simplify production and reduce manufacturing costs. Some board revisions were exclusive to PAL regions. All C64 motherboards were manufactured in Hong Kong.

IC locations changed frequently with each motherboard revision, as did the presence (or lack) of the metal RF shield around the VIC-II; PAL boards often had aluminized cardboard instead of a metal shield. The SID and VIC-II are socketed on all boards, but the other ICs may be socketed or soldered. The first production C64s, made from 1982 to early 1983, are known as "silver label" models due to the case having a silver-colored "Commodore" logo. The power LED had a silver badge reading "64" around it. These machines have only a five-pin video cable, and cannot produce S-Video. Commodore introduced the familiar "rainbow badge" case in late 1982, but many machines produced into early 1983 also used silver-label cases until the existing stock was used up. The original 326298 board was replaced in spring 1983 by the 250407 motherboard, which had an eight-pin video connector and added S-Video support. This case design was used until the C64C appeared in 1986. All ICs switched to plastic shells, but the silver-label C64s (notably the VIC-II) had some ceramic ICs. The case is made from ABS plastic, which may become brown with time; this can be reversed with retrobright.

The VIC-II was manufactured with 5-micrometer NMOS technology^[6], and was clocked at 17.73447 MHz (PAL) or 14.31818 MHz (NTSC). Internally, the clock was divided to generate the dot clock (about 8 MHz) and the two-phase system clocks (about 1 MHz; the pixel and system clock speeds differ slightly on NTSC and PAL machines). At such high clock rates the chip generated considerable heat, forcing MOS Technology to use a ceramic dual in-line package known as a CERDIP. The ceramic package was more expensive, but dissipated heat more effectively than plastic.

After a redesign in 1983, the VIC-II was encased in a plastic dual in-line package; this reduced costs substantially, but did not eliminate the heat problem.^[6] Without a ceramic package, the VIC-II required a heat sink. To avoid extra cost, the metal RFshielding doubled as the VIC's heat sink; not all units shipped with this type of shielding, however. Most C64s in Europe shipped with a cardboard RF shield coated with a layer of metal foil. The effectiveness of the cardboard was questionable; it acted instead as an insulator, blocking airflow and trapping heat generated by the SID, VIC, and PLA chips. The SID was originally manufactured using NMOS at 7 micrometers and, in some areas, 6 micrometers.^[6] The prototype SID and some early production models had a ceramic dual in-line package, but (unlike the VIC-II) are very rare; the SID was encased in plastic when production began in early 1982.

In 1986, Commodore released the last revision of the classic C64 motherboard. It was otherwise identical to the 1984 design, except for two 64-kilobit × 4-bit DRAM chips which replaced the original eight 64-kilobit × 1-bit ICs. After the release of the Commodore 64C, MOS Technology began to reconfigure the original C64's chipset to use HMOS technology. The main benefit of HMOS was that it required less voltage to drive the IC, generating less heat. This enhanced the reliability of the SID and VIC-II. The new chipset was renumbered 85xx to reflect the change to HMOS.

In 1987, Commodore released a 64C variant with a redesigned motherboard known as a "short board". The new board used the HMOS chipset, with a new 64-pin PLA chip. The "SuperPLA", as it was called, integrated discrete components and transistor–transistor logic (TTL) chips. In the last revision of the 64C motherboard, the 2114 4-bit-wide color RAM was integrated into the SuperPLA.

The C64 used an external power supply, a linear transformer with multiple taps differing from switch mode (presently used on PC power supplies). It was encased in epoxy resin gel, which discouraged tampering but increased the heat level during use. The design saved space in the computer's case, and allowed international versions to be more easily manufactured. The 1541-II and 1581 disk drives and third-party clones also have external power-supply "bricks", like most peripherals.

Commodore power supplies often failed sooner than expected. The computer reportedly had a 30-percent return rate in late 1983, compared to the 5–7 percent rate considered acceptable by the industry;^[105]Creative Computing reported four working C64s, out of seven.^[106] Malfunctioning power bricks were notorious for damaging the RAM chips. Due to their higher density and single supply (+5V), they had less tolerance for over-voltage. The usually-failing voltage regulator could be replaced by piggybacking a new regulator on the board and fitting a heat sink on top.^[107]

The original PSU on early-1982 and 1983 machines had a 5-pin connector which could accidentally be plugged into the computer's video output. Commodore later changed the design, omitting the resin gel to reduce costs. The following model, the Commodore 128, used a larger, improved power supply which included a fuse. The power supply for the Commodore REU was similar to that of the Commodore 128, providing an upgrade for customers purchasing the accessory.

• Microprocessor CPU:
  • MOS Technology 6510/8500 (the 6510/8500 is a modified 6502 with an integrated 6-bit I/O port)
  • Clock speed: 0.985 MHz (PAL) or 1.023 MHz (NTSC)
• Video: MOS Technology VIC-II 6567/8562 (NTSC), 6569/8565 (PAL)
  • 16 colors^[108]
  • Text mode: 40×25 characters; 256 user-defined chars (8×8 pixels, or 4×8 in multicolor mode); or extended background color; 64 user-defined chars with 4 background colors, 4-bit color RAM defines foreground color
  • Bitmap modes: 320×200 (2 unique colors in each 8×8 pixel block),^[109] 160×200 (3 unique colors + 1 common color in each 4×8 block)^[109]
  • 8 hardware sprites of 24×21 pixels (12×21 in multicolor mode)
  • Smooth scrolling, raster interrupts
• Sound: MOS Technology 6581/8580 SID
  • 3-channel^[108]synthesizer with programmable ADSR envelope
  • 8 octaves
  • 4 waveforms per audio channel: triangle, sawtooth, variable pulse, noise
  • Oscillator synchronization, ring modulation
  • Filtros programables: paso alto , paso bajo , paso banda y filtro de rechazo de banda.
• Entrada/Salida: Dos adaptadores de interfaz complejos 6526
  • E/S paralela de 16 bits
  • E/S serie de 8 bits
  • Reloj de 24 horas (AM/PM) con función de hora del día (TOD) y alarma programable ^{[ 110 ].}
  • Temporizadores de intervalo de 16 bits
• RAM:
  • 64 KiB, de los cuales 38 KiB estaban disponibles para programas BASIC.
  • 1024 nibbles ^{[ 96 ] : 262} RAM de color (memoria asignada para el almacenamiento de datos de color de la pantalla) ^{[ 111 ]}
  • Ampliable hasta 320 KiB con la unidad de expansión de RAM (REU) de 256 KiB del Commodore 1764 ; aunque solo 64 KiB son directamente accesibles; la REU se usa principalmente para el GEOS . También estaban disponibles las REU de 128 KiB y 512 KiB, diseñadas originalmente para el C128, pero requerían que el usuario comprara una fuente de alimentación más potente a un proveedor externo; con el 1764, esta venía incluida.

Creative Micro Designs también produjo una unidad REU de 2  MB para C64 y C128, llamada 1750 XL. La tecnología admitía hasta 16 MB, pero la de 2 MB era la de mayor capacidad fabricada oficialmente. También era posible ampliar la memoria hasta 16 MB mediante la CMD SuperCPU .

• MEMORIA DE SÓLO LECTURA:
  • 20 KB ( 9 KB Commodore BASIC 2.0; 7 KB KERNAL ; 4 KB generador de caracteres, que proporciona dos conjuntos de caracteres de 2 KB )

• Puertos de E/S: ^{[ 112 ]}
  • Ranura de expansión para cartucho ROM (ranura de 44 pines para conector de borde con líneas de bus de datos/direcciones de la CPU 6510 y señales de control, así como pines GND y de voltaje; ^{[ 113 ]} utilizada para módulos de programa y expansiones de memoria, entre otros)
  • Modulador de RF integrado con salida de antena de televisión mediante conector RCA . El canal seleccionado podía ajustarse desde el número 36 con el potenciómetro izquierdo.
  • Conector DIN de 8 pines que contiene salida de vídeo compuesto , salidas Y/C separadas y entrada/salida de audio. Esta es una versión en forma de herradura de 262° del conector, en lugar de la versión circular de 270°. Las primeras unidades C64 (con placa base Assy 326298) utilizan un conector DIN de 5 pines que transmite señales de vídeo compuesto y luminancia, pero carece de señal de croma. ^{[ 114 ]}
  • Serial bus (proprietary serial version of IEEE-488, 6-pin DIN plug) for CBM printers and disk drives
  • PET-type Commodore Datasette 300 baud tape interface (edge connector with digital cassette motor/read/write/key-sense signals), Ground and +5V DC lines. The cassette motor is controlled by a +5V DC signal from the 6510 CPU. The 9V AC input is transformed into unregulated 6.36V DC^[115] which is used to actually power the cassette motor.^[116]
  • User port (edge connector with TTL-level signals, for modems and so on; byte-parallel signals which can be used to drive third-party parallel printers, among other things, 17 logic signals, 7 ground and voltage pins, including 9 V AC)
  • 2× screwless DE9Mgame controller ports (compatible with Atari 2600 controllers), each supporting five digital inputs and two analog inputs. Available peripherals included digital joysticks, analog paddles, a light pen, the Commodore 1351 mouse, and graphics tablets such as the KoalaPad.
• Power supply:
  • 5 VDC and 9 V AC from an external "power brick", attached to a 7-pin female DIN-connector on the computer.^[117]

The 9 volt AC is used to supply power via a charge pump to the SID sound generator chip, provide 6.8 V via a rectifier to the cassette motor, a "0" pulse for every positive half wave to the time-of-day (TOD) input on the CIA chips, and 9 volts AC directly to the user-port. Thus, as a minimum, a 12 Vsquare wave is required. But a 9 Vsine wave is preferred.^[118][119]

Note that even if an I/O chip like the VIC-II only uses 64 positions in the memory address space, it will occupy 1,024 addresses because some address bits are left undecoded.^[120]

• 
  Commodore 1541 floppy drive
• 
  Commodore 1541C floppy drive
• 
  Commodore 1541-II floppy drive
• 
  Commodore 1530 Datasette
• 
  Commodore MPS-802 dot matrix printer
• 
  Commodore VIC-Modem
• 
  Commodore 1351 mouse
• 
  Commodore 1702 video monitor
• 
  Commodore 1581 3.5-inch double-sided floppy drive

Vertical integration was the key to keeping Commodore 64 production costs low. At the introduction in 1982, the production cost was US$135 and the retail price US$595. In 1985, the retail price went down to US$149 (US$450 today) and the production costs were believed to be somewhere between US$35–50 (c. US$100–150 today). Commodore would not confirm this cost figure. Dougherty of the Berkeley Softworks estimated the costs of the Commodore 64 parts based on his experience at Mattel and Imagic.

To lower costs, TTL chips were replaced with less expensive custom chips and ways to increase the yields on the sound and graphics chips were found. The video chip 6567 had the ceramic package replaced with plastic but heat dissipation demanded a redesign of the chip and the development of a plastic package that can dissipate heat as well as ceramic.^[6]

C64 enthusiasts were developing new hardware in 2008, including Ethernet cards,^[121] specially adapted hard disks and flash card interfaces (sd2iec).^[122] A-SID, which gives the C-64 a wah-wah effect, was introduced in 2022.^[123]

Los clones de C64 son ordenadores que imitan las funciones del Commodore 64. A mediados de 2004, tras una ausencia del mercado de más de 10 años, el fabricante de PC Tulip Computers (propietario de la marca Commodore desde 1997) anunció el C64 Direct-to-TV (C64DTV): un juego de TV con joystick basado en el C64, con 30 juegos en su ROM. Diseñado por Jeri Ellsworth , un diseñador de ordenadores autodidacta que había diseñado la implementación del C64 en el C-One , el C64DTV era similar a otras miniconsolas basadas en las modestamente exitosas Atari 2600 e Intellivision . El C64DTV se anunció en QVC en Estados Unidos para la temporada navideña de 2004. ^{[ 124 ]}

En 2015, Individual Computers produjo una placa base compatible con Commodore 64. Llamada C64 Reloaded, es un rediseño de la revisión 250466 de la placa base Commodore 64 con varias características nuevas. ^{[ 125 ]} La placa base está diseñada para colocarse en una carcasa C64 o C64C existente y vacía. Producida en cantidades limitadas, los modelos de este clon de Commodore 64 tienen zócalos mecanizados o ZIF en los que se colocan chips C64 personalizados. La placa contiene jumpers para aceptar revisiones de los chips VIC-II y SID y la capacidad de cambiar entre los sistemas de video PAL y NTSC . Tiene varias innovaciones, incluida la selección (a través de la tecla de restauración) de las ROM KERNAL y de caracteres, interruptor de reinicio incorporado en el interruptor de encendido y un conector S-Video para reemplazar el modulador de TV original . La placa base se alimenta mediante un convertidor CC-CC que utiliza 12 V CC procedentes de un adaptador de corriente, en lugar de la fuente de alimentación original (y propensa a fallos) del Commodore 64.

The C64 brand was reused in 1998 for the Web.it Internet Computer,^[126][127] a low-powered, Internet-oriented, all-in-one x86 PC running MS-DOS and Windows 3.1. It uses an AMD Élan SC400 SoC with 16 MB of RAM, a 3.5-inch floppy disk drive, 56k modem and PC Card.^[128] Despite its Commodore 64 nameplate, the C64 Web.it looks different and is only directly compatible with the original via included emulation software. PC clones branded C64x sold by Commodore USA, a company licensing the Commodore trademark,^[129][130] began shipping in June 2011.^[131] The C64x's case resembles the original C64 computer, but – like the Web.it – it is based on x86 architecture and is not compatible with the Commodore 64.

Several Commodore 64 games were released on the Nintendo Wii's Virtual Console service in Europe and North America. They were delisted from the service in August 2013.^[132]

British company Retro Games released two unofficial Linux-based emulation consoles based on the Commodore 64: THEC64 Mini in 2018 and the full size THEC64 in 2019. The name THEC64 – without a space between "The" and "C64" – is due to Retro Games not licensing the use of any Commodore trademarks including the C64 name; another consequence of this is that the Commodore key from the original keyboard is replaced with a THEC64 key.

THEC64 Mini is a decorative, half-size Commodore 64 with two USB and one HDMI port, and a mini USB connection to power the system. The keyboard is non-functional; the system is controlled by an included THEC64 joystick or a separate USB keyboard.^[133] The console uses the VICE emulator which can also load additional software ROMs.^[134]

The full-size THEC64 is the same size as the original Commodore 64, with a functional keyboard. Enhancements include VIC-20 emulation, two additional USB ports, and an upgraded joystick.

• 
  THEC64 Mini (top) next to an original C64
• 
  Full-size THEC64 in its original box

In December 2025, the Commodore 64 Ultimate was released by Commodore International. It is an FPGA-based remake of the Commodore 64, with added features such as HDMI output and the ability to load software over USB or a Wi-Fi or Ethernet network connection.^[135]

Commodore 64 emulators include the open sourceVICE, Hoxs64,^[136] and CCS64. An iPhone app was also released with a compilation of C64 ports.

The Commodore PET, introduced in July 2015, was an Android smartphone with Commodore 64 and Amiga emulation built-in.^[137]

• History of personal computers
• IDE64 – P-ATA interface cartridge for the C64
• Keyboard computer
• List of Commodore 64 games
• SuperCPU – CPU upgrade for C64 and C128

• Commodore 64 history, manuals, and photos (Archived September 5, 2012, at the Wayback Machine)
• C64-Wiki (wiki-based encyclopaedia)
• C64.com (C64 game database)
• Lemon64 (C64 fanbase)
• Csdb.dk (Commodore Scene/Software Database)
• Extensive collection of information on C64 programming
• A History of Gaming Platforms: The Commodore 64 from October 2007
• A Commodore 64 Web Server Using Contiki v2.3* "Variations on the Commodore 64". Commodoremagazine. Archived from the original on May 4, 2010. Retrieved January 24, 2011.
• Design Case History: The Commodore 64, IEEE Spectrum, March 1985
• Comparing different unit sales analyses