Commodore 64

Commodore 64
Commodore 64
Type Home computer
Release date August 1982[1]
Discontinued April 1994
Operating system Commodore KERNAL/
Commodore BASIC 2.0
CPU MOS Technology 6510
@ 1.023 MHz (NTSC version)
@ 0.985 MHz (PAL version)
Memory 64 kB RAM + 20 kB ROM
Graphics VIC-II (320 × 200, 16 colors, sprites, raster interrupt)
Sound SID 6581 (Osc, Wave, Filter, ADSR, Ring)
Connectivity 2× CIA 6526 Joystick, Power, Cartridge, RF, A/V, IEEE-488 Floppy/Printer, Digital tape, GPIO/RS-232
Predecessor Commodore VIC-20
Successor Commodore 128

The Commodore 64 is an 8-bit home computer introduced by Commodore International in January 1982. Volume production started in the spring of 1982, with machines being released on to the market in August at a price of US$595.[2][3] Preceded by the Commodore VIC-20 and Commodore PET machines, the C64 features 64 kilobytes (65,536 bytes) of RAM, hence the name, and had favourable sound and graphical specifications when compared to well known contemporary systems such as the Apple II, particularly as the price was well below that demanded by Apple. It is commonly known as the C64 or C=64 (after the graphic logo on the case) and occasionally as the CBM 64 (for Commodore Business Machines), or VIC-64.[4] It has also been nicknamed the "breadbox" and "bullnose" due to the shape and color of its initial casing.[citation needed]

During the C64's lifetime, sales totalled between 12.5 and 17 million units, making it the best-selling single personal computer model of all time.[5][6] For a substantial period of time (1983–1986), the C64 dominated the market with between 30% and 40% share and 2 million units sold per year,[7] outselling the IBM PC clones, Apple Inc. computers, and Atari 8-bit family 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."[8]

Part of its success was because it was sold in retail stores instead of electronics stores. Commodore produced many of its parts in-house to control supplies and cost. It is sometimes compared to the Ford Model-T automobile for its role in bringing a new technology to middle-class households via creative mass-production.[9]

Approximately 10,000 commercial software titles were made for the Commodore 64 including development tools, office productivity applications, and games.[10] C64 emulators allow anyone with a modern computer, or a compatible game console, to run these programs today. The C64 is also credited with popularizing the computer demo scene and is still used today by some computer hobbyists.[11]



The Commodore 64 startup screen

In January 1981, MOS Technology, Inc., Commodore's integrated circuit design subsidiary, initiated a project to design the graphic and audio chips for a next generation video game console. Design work for the chips, named MOS Technology VIC-II (graphics) and MOS Technology SID (audio), was completed in November 1981.[2]

Commodore then began a game console project that would use the new chips—called the Ultimax or alternatively the Commodore MAX Machine, engineered by Yash Terakura from Commodore Japan. This project was eventually cancelled after just a few machines were manufactured for the Japanese market.

At the same time, Robert "Bob" Russell (system programmer and architect on the VIC-20) and Robert "Bob" Yannes (engineer of the SID) were critical of the current product line-up at Commodore, which was a continuation of the Commodore PET line aimed at business users. With the support of Al Charpentier (engineer of the VIC-II) and Charles Winterble (manager of MOS Technology), they proposed to Commodore CEO Jack Tramiel a true low-cost sequel to the VIC-20. Tramiel dictated that the machine should have 64 kB of RAM. Although 64 kB of DRAM cost over US$ 100 at the time, he knew that DRAM prices were falling, and would drop to an acceptable level before full production was reached. In November, Tramiel set a deadline for the first weekend of January, to coincide with the 1982 Consumer Electronics Show.[2]

The product was codenamed the VIC-40 as the successor to the popular VIC-20. The team that constructed it consisted of Bob Russell, Bob Yannes and David A. Ziembicki. The design, prototypes and some sample software was finished in time for the show, after the team had worked tirelessly over both Thanksgiving and Christmas weekends.

The machine incorporated Commodore BASIC 2.0 in ROM and available immediately at startup.

When the product was to be presented, the VIC-40 product was renamed C64 in order to fit into the current Commodore business products lineup which contained the P128 and the B256, both named by a letter and their respective memory size.

The C64 made an impressive debut at the January 1982 Winter 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 $595?'" The answer, as it turned out, was vertical integration; thanks to Commodore's ownership of MOS Technology's semiconductor fabrication facilities, each C64 had an estimated production cost of only US$ 135.

Winning the market war

Games cartridges for Radar Rat Race and International Soccer

The C64 faced a wide range of competing home computers at its introduction in August 1982.[1] With an impressive price coupled with the C64's more flexible hardware, it quickly out-sold many of its competitors. In the United States the greatest competitors to the C64 were the Atari 8-bit 400 and 800, and the Apple II. The Atari 400 and 800 were very similar in hardware terms, but used custom chips for graphics and sound, and so were very expensive to build. The Apple IIe, the latest in the aging Apple II line had higher resolution graphics modes than the C64,[12][13] but due to poor color support they were rarely used[citation needed], so in practice the C64's 16-color (4-bit) graphics and sound abilities outmatched them at the time of its release. Upgrade capability for the Apple II was granted by internal expansion slots, while the C64 had only a single external cartridge port for bus expansion. However, the Apple used its expansion slots for interfacing to 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, leaving the cartridge port free. In practice though, the cartridge port was mainly taken up with a fast loader cartridge used to remedy the 64's slow disk transfer rate.

All four machines had similar standard memory configurations in the years 1982/83: 48 kB for the Apple II+[14] (upgraded within months of C64's release to 64K with the Apple IIe) and 48K for the Atari 800.[15] At upwards of US$ 1200,[16] the Apple II was more than twice as expensive, while the Atari 800 cost US$899. One key to the C64's success was Commodore's aggressive marketing tactics, and they were quick to exploit the relative price/performance divisions between its competitors with a series of television commercials after the C64's launch in late 1982.[17]

Commodore sold the C64 not only through its network of authorized dealers, but also placed it on the shelves of department stores, discount stores, and toy stores. The C64 had a built-in RF modulator and thus could be plugged into a 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 baseband composite video and thus could be plugged into a specialized monitor for a sharper picture. Unlike the IIe, the C64's baseband NTSC output capability included separate luminance/chrominance signal output equivalent to (and electrically compatible with) S-Video, for connection to the popular Commodore 1702 monitor.

Aggressive pricing of the C64 is considered to be a major catalyst in the North American video game crash of 1983. In January 1983, Commodore offered a US$ 100 rebate in the United States on the purchase of a C64 to anyone trading in another computer or video game console. To take advantage of this rebate, some mail-order dealers and retailers offered a Timex Sinclair 1000 for as little as US$ 10 with purchase of a C64, so 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 the exit of Texas Instruments and other smaller competitors from the field. The price war with Texas Instruments was seen as a personal battle for Commodore president Jack Tramiel; 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.[18] In parts of the US in the late 1980s, new C64s could be purchased in retail chains for a little more than US$ 100.

In 1984, Commodore released the Commodore Plus/4. The Plus/4 offered a higher-color display, a better implementation of BASIC (V3.5), and built-in software in what was positioned as an inexpensive business oriented system. However, it was incompatible with the C64, and Amstrad and other PC and CP/M clones rendered the limited business software and lack of compactness of the multiple-lead Plus/4 system of marginal value. The Plus/4 lacked hardware sprite capability and had much poorer sound, thus seriously under-performing in two of the areas that had made the C64 successful.

In Europe, the primary competitors to the C64 were the British-built Sinclair ZX Spectrum, BBC Microcomputer and the Amstrad CPC 464. In the UK, the Spectrum had been released a few months ahead of the C64, and was selling for less than half the price. The Spectrum quickly became the market leader and Commodore had an uphill struggle against the Spectrum. The C64 debuted at £399 in early 1983, while the Spectrum cost £175. The C64 would later rival the Spectrum in popularity in the latter half of the 1980s, eventually outselling the Spectrum after 1985.

Despite a few attempts by Commodore to discontinue the C64 in favor of other, higher priced machines, constant demand made its discontinuation a hard task. By 1988, Commodore was selling 1.5 million C64s worldwide.[19] Although demand for the C64 dropped off in the US by 1990, it continued to be popular in the UK and other European countries. In the end, economics, not obsolescence, sealed the C64's fate. In March 1994, at CeBIT in Hanover, Germany, Commodore announced that the C64 would be finally discontinued in 1995. Commodore stated that the C64's disk drive was more expensive to manufacture than the C64 itself. Although Commodore had planned to discontinue the C64 by 1995, the company filed for bankruptcy a month later, in April 1994.[20]

The C64 family

Commodore 64C with 1541-II floppy disk drive and 1084S monitor displaying television-compatible S-video

1982: Commodore released the Commodore MAX Machine in Japan. It is called the Ultimax in the US, and VC-10 in Germany. The MAX was intended to be a game console with limited computing capability, and was based on a very 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.

1983 saw Commodore attempt to compete with the Apple II's hold on the US education market with the Educator 64,[21] essentially a C64 and "greenscale" 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.

In 1984, Commodore released the SX-64, a portable version of the C64. The SX-64 has the distinction of being the first full-color portable computer. The base unit featured a 5 in (130 mm) CRT and an integrated 1541 floppy disk drive. The SX-64 did not have a cassette connector.

Commodore, specifically two designers; Fred Bowen and Bil Herd, were determined to avoid the problems of the Plus/4, making sure that the eventual successors to the C64—the Commodore 128 and 128D computers (1985)—were as good as, and fully compatible with the original, as well as offering a host of improvements (such as a structured BASIC with graphics and sound commands, 80-column display capability, and full CP/M compatibility). The decision to make the Commodore 128 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) show in Las Vegas. 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 1986, Commodore released the Commodore 64C (C64C) computer, which was functionally identical to the original, but whose exterior design was remodeled in the sleeker style of the Commodore 128 and other contemporary design trends. The modifications to the C64 line were more than skin deep in the C64C with new versions of the SID, VIC and I/O chips being deployed—with the core voltage reduced from 12 V to 9 V. In the United States, the C64C was often bundled with the third-party GEOS GUI-based operating system. The Commodore 1541 disk drive received a matching face-lift resulting in the 1541c. Later a smaller, sleeker 1541-II model was introduced along with the 800 kB 3.5-inch microfloppy 1581.

In 1990, the C64 was re-released in the form of a game console, called the C64 Games System (C64GS). A simple modification to the C64C's motherboard was made to orient the cartridge connector to a vertical position. This allowed cartridges to be inserted from above. A modified ROM replaced the BASIC interpreter with a boot screen to inform the user to insert a cartridge. It was designed to rival the Nintendo Entertainment System and the Sega Master System but it suffered from very low sales compared to its rivals and it was another commercial failure for Commodore, and it was never released outside of Europe.

In 1990, an advanced successor to the C64, the Commodore 65 (also known as the "C64DX"), was prototyped, but the project was canceled by Commodore's chairman Irving Gould in 1991. The C65's specifications were very good for an 8-bit computer. For example, it could display 256 colors on screen, while OCS based Amigas could only display 64 in HalfBrite mode (32 colors and half-bright transformations); the HAM mode on the Amiga allowed all 4096 colors of the 12 bit color system, but it was awkward to use and had restrictions on color combinations between adjacent pixels. Although no specific reason was given for the C65's cancellation, it would have competed in the marketplace with Commodore's lower end Amigas and the CDTV.

C64 clones

In the middle of 2004, after an absence from the marketplace of more than 10 years, PC manufacturer Tulip Computers BV (owners of the Commodore brand since 1997) announced the C64 Direct-to-TV (C64DTV), a joystick-based TV game based on the C64 with 30 games built into ROM. Designed by Jeri Ellsworth, a self-taught computer designer who had earlier designed the modern C-One C64 implementation, the C64DTV was similar in concept to other mini-consoles based on the Atari 2600 and Intellivision which had gained modest success earlier in the decade. The product was advertised on QVC in the United States for the 2004 holiday season. Some users have installed 1541 floppy disk drives, hard drives, second joysticks and keyboards to these units, which give the DTV devices nearly all of the capabilities of a full Commodore 64. The DTV hardware is also used in the mini-console/game Hummer, sold at RadioShack mid-2005.

C64 enthusiasts still develop new hardware, including Ethernet cards,[22] specially adapted hard disks and Flash Card interfaces (sd2iec[23]).

Brand re-use

PC clones branded as "C64" in May 2011 are planned by Commodore USA, LLC, a company licensing the Commodore trademark.[24][25] and began shipping units in June 2011.[26][27] This "C64x" has a case resembling the original C64 computer, but it is based on X86 architecture. The machine is a nettop-spec computer which comes with a 1.8 GHz 64-bit dual core D525 Atom processor, Nvidia ION2 onboard graphics, Wi-Fi, hard disk drive and an optional built-in DVD or Blu-ray player.

It is shipping initially with Ubuntu 10.10 Desktop Edition. Commodore USA claims they are also developing their own Linux derivative called Commodore OS, that along with a classic games package, is planned to ship out to early adopters. There will be no hardware compatibility with the original C64, with software compatibility provided through the use of an emulator.


In 1982, the C64's graphics and sound capabilities were rivaled only by the Atari 8-bit family, and appeared exceptional when compared with the widely publicised Atari VCS and Apple II.

The C64 is often credited with starting the computer subculture known as the demoscene (see Commodore 64 demos). The C64 lost its top position among demo coders when the 16-bit Commodore Amiga and Atari ST were released in 1985, however it still remained a very popular platform for demo coding up to the early 90s[citation needed].

It is still being actively used in the demo scene,[28] especially for music (its sound chip even being used in special sound cards for PCs, and the Elektron SidStation synthesizer). Unfortunately, the differences between PAL and NTSC C64s caused compatibility problems between US/Canadian C64s and those from most other countries. The vast majority of demos run only on PAL machines.

Even though other computers quickly caught up with it, the C64 remained a strong competitor to the later consoles Nintendo Entertainment System and Sega Master System, thanks in part to its by-then established software base, especially outside of North America, where it comprehensively outsold the NES.


The Simons' BASIC start-up screen. Note the altered background and text colours (vs the ordinary C64 blue tones), and the 8 kB reduction of available BASIC program memory due to the address space used by the cartridge.

As was common for home computers of the early 1980s, the C64 incorporated a ROM based version of the BASIC programming language. There was no "operating system" as such. The kernal was accessed via BASIC commands. The disk drive had its own microprocessor (like in the Atari 800). This meant that no memory space had to be dedicated to run the drive, as remained the case with earlier systems like the Apple II.

Commodore BASIC 2.0 was used instead of the more advanced BASIC 4.0 from the PET series, since its users were not expected to need the disk-oriented enhancements of BASIC 4.0. "The choice of BASIC 2.0 instead of 4.0 was made with some soul-searching, not just at random. The typical user of a C64 is not expected to need the direct disk commands as much as other extensions, and the amount of memory to be committed to BASIC was to be limited. We chose to leave expansion space for color and sound extensions instead of the disk features. As a result, you will have to handle the disk in the more cumbersome manner of the 'old days'."[29]

The version of BASIC was limited and did not include specific commands for sound or graphics manipulation, instead required users to use the "POKE" commands to access the graphics and sound chip registers directly. In order to provide extended commands including graphics and sound Commodore produced two different cartridge-based extension to BASIC 2.0 — Simons' BASIC and Super Expander 64.

Other languages available for the C64 included Pascal, LOGO, Forth, and FORTRAN. Compiled versions of BASIC such as Petspeed 2 (from Commodore) and Turbo Lightning (Ocean Software) were also available.

But most programs were written in assembly language, using a machine code monitor or an assembler. This maximised speed and minimised memory use.

Alternative operating systems

A number of third party operating systems have been developed for the C64.

GEOS for the Commodore 64

As well as the original GEOS, two third-party GEOS-compatible operating systems have been written: Wheels and GEOS megapatch. Both of these require hardware upgrades to the original C64.

Several other operating systems are or have been available, including WiNGS OS, the Unix-like LUnix, operated from a command-line, and the embedded systems OS Contiki, with full GUI. Other less well known OSes include ACE, Asterix, DOS/65 and GeckOS.

A version of CP/M was released, but this required the addition of an external Z80 processor to the expansion bus, so is not considered a true C64 OS. Furthermore, the Z80 processor was underclocked to be compatible with the C64's memory bus, so performance was poor compared to other CP/M implementations. C64 CP/M and C128 CP/M both suffered a lack of software: although most commercial CP/M software would technically run on these systems, software media was incompatible between platforms. The low usage of CP/M on Commodores meant that software houses saw no need to invest in mastering versions for the Commodore filesystem.

Networking software

During the 1980s, the Commodore 64 was used to run numerous Bulletin Board Systems using software packages such as Bizarre 64, Blue Board and Color 64, often with sysop-made modifications. These boards sometimes were used to distribute cracked software.

There were also 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 continues to operate its AOL service for the IBM PC and Apple Macintosh today. Q-Link was a modified version of the PlayNET system, which Control Video Corporation (CVC, later renamed Quantum Computer Services) licensed.

The Quantum Link networking service became America Online which became AOL-Time Warner which was then contracted to AOL.

Online gaming

The original interactive game on the micro was M.U.D, the "Multi User Dungeon", a text based adventure / RPG programme based on the original Adventure wriiten by Tony Crowther for the DEC PDP-9. Written for British Telecom on Compunet, the game was expanded to Compuserve in US. This text based adventure game allowed real time conversations and combats (in text) via the large commercial BBS.

Don Daglow and the Stormfront game design team began working with AOL on original online games in 1987, in both text-based and graphical formats. At the time AOL was a Commodore 64 only online service, known as Quantum Computer Services, with just a few thousand subscribers, and was called Quantum Link. Online graphics in the late 1980s were severely restricted by the need to support modem data transfer rates as slow as 300 bits per second (bit/s). During the early 1990s, commercial use of the internet was limited by NSFNET acceptable use policies. Consequently, early online games like Legends of Future Past, Neverwinter Nights, GemStone III, Dragon's Gate, and Federation relied heavily on proprietary services such as CompuServe, America Online, and GEnie for distribution.

The first graphical character-based interactive environment was 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 very basic, its use of online avatars (already well established off-line by Ultima and other games) and combination of chat and graphics was revolutionary.


CPU and memory

The C64 uses an 8-bit MOS Technology 6510 microprocessor. This is a close derivative of the 6502 with an added 6-bit internal I/O port that in the C64 is used for two purposes: to bank-switch the machine's ROM in and out of the processor's address space, and to operate the datasette tape recorder.

The C64 has 64 kB of RAM, of which 38 kB are available to built-in Commodore BASIC 2.0 on start up.

There is 20 kB of ROM, made up of the BASIC interpreter, the kernal, and the character ROM. As the processor could only address 64 kB at a time, the ROM was mapped into memory and only 38 911 bytes of RAM were available at start up.

If a program did not use the BASIC interpreter, RAM could be mapped over the ROM locations. However, this meant that the character ROM would not be available, and nothing could be seen. This was solved by copying the character ROM into RAM. This had two benefits ; the standard typeface could be re-written, and character codes could be re-written as picture elements in a picture.

Most C64 games were written in this way, using low resolution, which required much less processor time and saved memory. Furthermore, picture elements could be re-used, saving even more precious memory. The same technique was used in systems like the NES.


The graphics chip, VIC-II, features 16 colors, 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.

Most screen shots show borders around the screen, which is a feature of the VIC-II chip. By utilising interrupts to reset various hardware registers on precise timings it was possible to place graphics within the borders and thus utilise the full screen.[30]

There were two low resolution and two bit mapped modes. Multi-colour bitmapped mode had an addressable screen of 160 x 200 pixels, with a maximum of four colours per 8 x 8 character block. High resolution bitmapped mode had an addressable screen of 320 x 200 pixels, with a maximum of two colours per 8 x 8 character block.

Multicolour low resolution had a screen of 160 x 200 pixels, 40 x 25 addressable with fours colours per 8 x 8 character block. High resolution "low resolution" had a screen of 320 x 200 pixels, 40 x 25 addressable with two colours per 8 x 8 character block.

Most videogames used Multicolour low resolution. This allowed only character block - by character block animation because of the limited addressable space. This wasn't an issue however, as the video chip automated sprites and vertical and horizontal scrolling pixel by pixel and worked smooth and fast regardless of the video mode. Some animation (for instance, bullets), used character animation, where sprites were not available.


The SID chip has three channels, each with its own ADSR envelope generator, ring modulation and filter capabilities. Bob Yannes developed the SID chip and later co-founded synthesizer company Ensoniq. Yannes criticized other contemporary computer sound chips as "primitive, obviously... designed by people who knew nothing about music". Often the game music became a hit of its own among C64 users. Well-known composers and programmers of game music on the C64 are Rob Hubbard, David Whittaker, Chris Hülsbeck, Ben Daglish, Martin Galway, David Dunn and Kjell Nordbø among many others. Due to the chip's three channels, chords are played as arpeggios, coining the C64's characteristic lively sound. It was also possible to continuously update the master volume with sampled data to enable the playback of 4-bit digitized audio. As of 2008, it became possible to play four channel 8-bit audio samples, 2 SID channels and still use filtering.

There are two versions of the SID chip, the 6581 and the 8580. The MOS Technology 6581 was used in the original "breadbox" C64s, the early versions of the C64C and the Commodore 128. The 6581 was replaced with the MOS Technology 8580 in 1987. The 6581 sound quality is a little more crisp, and many Commodore 64 fans prefer its sound. The main difference between the 6581 and the 8580 is the supply voltage. The 6581 uses a 12 volt supply - the 8580, a nine volt supply. A modification can be made to use the 6581 in a C64C board (which uses the nine volt chip).

The SID chip has a distinctive sound which has retained a following of devotees to such a degree, that a number of audio enthusiasts and companies have designed SID-based products as add-ons for the C64, x86 PCs, and standalone or MIDI music devices such as the Elektron SidStation. These devices use chips taken from excess stock, or removed from used computers.

In 2007, Timbaland's extensive use of the SidStation led to the 2007 Timbaland plagiarism controversy around his tracks Block Party and Do It (written for Nelly Furtado).

Hardware revisions

Cost reduction was the driving force behind the C64's motherboard revisions. Reducing manufacturing costs was vitally important to Commodore's survival during the price war and leaner years of the 16-bit era. The C64's original (NMOS based) motherboard would go through two major redesigns, (and numerous sub-revisions) exchanging positions of the VIC-II, SID and PLA chips. Initially, a large portion of the cost was eliminated by reducing the number of discrete components, such as diodes and resistors, which enabled the use of a smaller printed circuit board. The case is made from ABS plastic which may become brown with time. This can be reversed by using the public domain chemical mix "Retr0bright".

An early C64 motherboard (Rev A PAL 1982).
A C64C motherboard ("C64E" Rev B PAL 1992).


The VIC-II was manufactured with 5 micrometer NMOS technology[2] and was clocked at either 17.73447 MHz (PAL) or 14.31818 MHz (NTSC). Internally, the clock was divided down to generate the dot clock (about 8 MHz) and the two-phase system clocks (about 1 MHz; the exact pixel and system clock speeds are slightly different between NTSC and PAL machines). At such high clock rates, the chip generated a lot of heat, forcing MOS Technology to use a ceramic DIL package (called a "CERDIP"). The ceramic package was more expensive, but it dissipated heat more effectively than plastic.

After a redesign in 1983, the VIC-II was encased in a plastic Dual Inline Package, which reduced costs substantially, but it did not totally eliminate the heat problem.[2] Without a ceramic package, the VIC-II required the use of a heat sink. To avoid extra cost, the metal RF shielding doubled as the heat sink for the VIC, although not all units shipped with this type of shielding. Most C64s in Europe shipped with a cardboard RF shield, coated with a layer of metal foil. The effectiveness of the cardboard was highly questionable, and worse still it acted as an insulator, blocking airflow which trapped heat generated by the SID, VIC, and PLA chips.

The SID was manufactured using NMOS at 7 and in some areas 6 micrometers.[2] The prototype SID and some very early production models featured a ceramic Dual Inline Package, but unlike the VIC-II, these are extremely rare as the SID was encased in plastic when production started in early 1982.


In 1986, Commodore released the last revision to the classic C64 motherboard. It was otherwise identical to the 1984 design, except for the two 64 kilobit × 4 bit DRAM chips that replaced the original eight 64 kilobit × 1 bit ICs.

After the release of the C64C, MOS Technology began to reconfigure the C64's chipset to use HMOS production technology. The main benefit of using HMOS was that it required less voltage to drive the IC, which consequently generates less heat. This enhanced the overall reliability of the SID and VIC-II. The new chipset was re-numbered to 85xx in order to reflect the change to HMOS.

In 1987, Commodore released C64Cs with a totally redesigned motherboard commonly known as a "short board". The new board used the new HMOS chipset, featuring a new 64-pin PLA chip. The new "SuperPLA", as it was dubbed, integrated many discrete components and TTL chips. In the last revision of the C64C motherboard, the 2114 color RAM was integrated into the SuperPLA.

Power supply

The C64 used an external power supply, a conventional transformer with multiple tappings (as opposed to switch mode, the system used today [2011] on PC power supplies), encased in a gel (epoxy resin) which tended to increase the heat level when running.

This saved space within the computer's case and allowed international versions to be more easily manufactured. The 1541-II and 1581 disk drives, along with various third-party clones, also came with their own external power supply "bricks", as did most peripherals leading to a "spaghetti" of cables and the use of numerous double adapters by users.

These power supplies were notorious for failing over time.[31]

Commodore later changed the design, omitting the gel.

The proprietary design usually led to "freezing" after a few hours, so many serious users - such as programmers - used their own dual circuit power supplies instead[dubious ][citation needed].


Internal hardware

I/O ports and power supply

Commodore 64 ports (from left: Cartridge, RF-adj, RF, A/V, 488, Tape, User + Joy1, Joy2, Power)
  • I/O ports:[36]
    • Cartridge expansion slot (slot for edge connector with 6510 CPU address/data bus lines and control signals, as well as GND and voltage pins; used for program modules and memory expansions, among others)
    • Integrated RF modulator antenna output via a RCA connector. The used channel could be adjusted from number 36 with the potentiometer to the left.
    • 8-pin DIN connector containing composite video output, separate Y/C outputs and sound input/output. Beware that this is the 270° (horseshoe) version of the plug, not the 360° circular version. Also note that some early C64 units use a 5-pin DIN connector that carries composite video and luminance signals, but lacks a chroma signal.[37]
    • Serial bus (serial version of IEEE-488, 6-pin DIN plug) for CBM printers and disk drives
    • PET-type Commodore Datassette 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 6502 CPU. The 9 V AC input is transformed into unregulated 6.36 V DC[38] which is used to actually power the cassette motor.[39]
    • 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 9V AC)
    • 2 × screwless DE9M game 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:
    • 5V DC and 9VAC from an external "power brick", attached to a 7-pin female DIN-connector on the computer.[40]

The 9 volt AC is used to supply power via a charge pump to the SID sound generator chip, provide 6.8V 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 V square wave is required. But a 9 V sine wave is preferred.[41][42]


See also


  1. ^ a b July 1982 Commodore brochure
  2. ^ a b c d e f Perry, Tekla S.; Wallich, Paul. "Design case history: The Commodore 64". IEEE Spectrum, March 1985.
  3. ^ "MayhemUK Commodore 64 archive".  090918
  4. ^ VIC 64 Användarmanual. Image of Swedish edition of the VIC 64 user's manual. Retrieved on 2007-03-12.
  5. ^ Reimer, Jeremy. "Personal Computer Market Share: 1975-2004". Retrieved 2009-07-17. 
  6. ^ "How many Commodore 64 computers were sold?". Retrieved 2011-02-01. 
  7. ^ Reimer, Jeremy. "Total share: 30 years of personal computer market share figures". Ars Technica. Retrieved 2008-09-13. 
  8. ^ Naman, Mard (September 1989). "From Atari's Oval Office An Exclusive Interview With Atari President Sam Tramiel". STart (San Francisco: Antic Publishing) 4 (2): p. 16. 
  9. ^ Kahney, Leander (2003-09-09). "Grandiose Price for a Modest PC". CondéNet, Inc. Retrieved 2008-09-13. 
  10. ^ "Impact of the Commodore 64: A 25th Anniversary Celebration". Computer History Museum. Retrieved 2008-09-13. 
  11. ^ Swenson, Reid C. (2007). "What is a Commodore Computer? A Look at the Incredible History and Legacy of the Commodore Home Computers". OldSoftware.Com. Retrieved 2007-11-19. 
  12. ^ "PC - Model 5150". Retrieved 2008-09-13. 
  13. ^ "APPLE IIe". Retrieved 2008-09-13. 
  14. ^ "APPLE II+". Retrieved 2008-09-13. 
  15. ^ "Atari 800". Retrieved 2008-09-13. 
  16. ^ Apple II History Chap 6
  17. ^ "Commodore Commercials". Retrieved 2008-09-13. 
  18. ^ Remier, Jeremy. "A history of the Amiga, part 4: Enter Commodore". Retrieved 2008-08-04. 
  19. ^ "Computer Chronicles: Interview with Commodore president with Max Toy". 2007-07-24. Retrieved 2007-07-24. 
  20. ^ Amiga Format News Special. "Commodore at CeBIT '94". Amiga Format, Issue 59, May 1994.
  21. ^ "The Educator 64 & Commodore PET 64 (aka C=4064)". Retrieved 2008-09-13. 
  22. ^ Dunkels, Adam. "The Final Ethernet - C64 Ethernet Cartridge". Retrieved 2008-09-13. 
  23. ^ "SD2IEC on c64 wiki". 
  24. ^ "Iconic Commodore 64 All Set For Comeback". 
  25. ^ "Recreating the Legendary Commodore 64". 
  26. ^ "Commodore USA begins shipping replica C64s next week, fulfilling your beige breadbox dreams". 
  27. ^ "Commodore USA site showing assembly and boxed units ready for shipping". 
  28. ^
  29. ^ C64 basic introduction, Pg. 65, Commodore Magazine, Aug 1982
  30. ^ Ojala, Pasi. "Opening the Borders". Retrieved 2008-09-13. 
  31. ^ Mace, Scott (November 13, 1983). "Commodore 64: Many unhappy returns". InfoWorld (Popular Computing Inc.) 5 (46): p. 23. ISSN 0199-6649. 
  32. ^ Rautiainen, Sami. "Programmers_Reference". Retrieved 2011-03-23. 
  33. ^ Rautiainen, Sami. "Programmers_Reference". Retrieved 2011-03-23. 
  34. ^ MOS 6526 CIA datasheet (PDF format)
  35. ^ Rautiainen, Sami. "Service_Manual: RAM Control Logic.". Retrieved 2011-03-13. 
  36. ^ "empty".  090505
  37. ^ Carlsen, Ray. "C64 video port". Retrieved 2008-09-13. 
  38. ^ "250469 rev.A right".  100610
  39. ^ "250469 rev.A left".  100610
  40. ^ "Commodore C64 Power Supply Connector Pinout - AllPinouts".  090505
  41. ^ "Commodore-64 BN/E 250469 schematic".  090519
  42. ^ "Commodore-64 BN/E 250469 schematic".  090519


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