# Commodore PET
**Commodore PET** (Personal Electronic Transactor) was a personal computer introduced by Commodore in 1977 as a ready-to-run machine with a MOS 6502 processor, BASIC in ROM, a built-in monitor, and cassette storage. Appearing before the Apple II and the Radio Shack TRS-80, it was among the first personal computers[1](https://americanhistory.si.edu/collections/object/nmah_334374), and together with those two machines it forms what retrocomputing writers call the "1977 Trinity" of ready-to-run home computers[2](http://www.righto.com/2025/04/commodore-pet-repair.html). The first model, the PET 2001, included four kilobytes of memory, cost $495, and was fully functional out of the box[1](https://americanhistory.si.edu/collections/object/nmah_334374).
| Key fact | Detail |
|---|---|
| First shown | Chicago Consumer Electronics Show, January 1977, months before the TRS-80 and Apple II[3](https://nosher.net/archives/computers/pet_brochure_1977_11_003?idx=Peddle) |
| Core hardware | 1 MHz MOS 6502, 4 KB or 8 KB RAM expandable to 32 KB, 14 KB ROM with BASIC and a machine-language monitor[1](https://americanhistory.si.edu/collections/object/nmah_334374) • [4](https://vintagecomputer.ca/files/Commodore/marketing/Brochure-Commodore%20PET%202001.pdf) |
| Display | Built-in 9-inch green phosphor screen, 40 characters by 25 lines, 8x8 dot matrix characters[4](https://vintagecomputer.ca/files/Commodore/marketing/Brochure-Commodore%20PET%202001.pdf) • [5](https://bitsavers.trailing-edge.com/pdf/datapro/datapro_reports_70s-90s/Commodore/M09-160-10_8006_Commodore_PET.pdf) |
| Launch prices | $495 mail order for 4 KB, then $595; $795 for 8 KB[6](https://www.commodore.ca/commodore-products/commodore-pet-the-worlds-first-personal-computer/) • [3](https://nosher.net/archives/computers/pet_brochure_1977_11_003?idx=Peddle) |
| Character set | PETSCII, a non-standard ASCII variant with two complete character sets: upper/lower-case letters and upper-case/block graphics[6](https://www.commodore.ca/commodore-products/commodore-pet-the-worlds-first-personal-computer/) |
| Total sales | About 219,000 units by discontinuation in 1982, or about 242,000 Commodore systems of all types by July 1982, depending on the source[7](https://8bitarchitect.net/history/the-commodore-pet-a-wooden-box-a-six-month-deadline-and-the-machine-that-made-commodore/) • [8](https://bitsavers.trailing-edge.com/pdf/datapro/datapro_reports_70s-90s/Commodore/M09-160-10_8207_Commodore_PET4001.pdf) |
| Collector value | An early boxed PET 2001, serial number 77 of the first 100, sold for US$6,784 at RR Auction on 17 March 2022[9](https://8bitarchitect.net/machines/commodore-pet-2001/) |
## Origins and design
The PET grew directly out of Commodore's 1976 purchase of [MOS Technology](https://www.edgepedia.org/mos-technology). MOS had undercut Motorola and Intel on microprocessor price in 1975 with the 6502, whose design came from ex-[Motorola 6800](https://www.edgepedia.org/motorola-6800) team members who believed they could improve on the 6800[7](https://8bitarchitect.net/history/the-commodore-pet-a-wooden-box-a-six-month-deadline-and-the-machine-that-made-commodore/) • [10](https://www.atarimagazines.com/compute/issue1/3194_1_A_COMMODORE_PERSPECTIVE.php). Chuck Peddle believed a personal computer was the next step and had tried without luck to interest Radio Shack in selling one; Commodore bought MOS in the autumn of 1976[7](https://8bitarchitect.net/history/the-commodore-pet-a-wooden-box-a-six-month-deadline-and-the-machine-that-made-commodore/).
The machine that became the PET was the KIM-1, MOS's single-board 6502 demonstrator, put in a case with a keyboard, a monitor, and more memory[3](https://nosher.net/archives/computers/pet_brochure_1977_11_003?idx=Peddle). The design team itself described the PET as having "effectively graduated out of the KIM I", with the whole project taking less than a year from the first go-ahead[11](https://www.commodore.ca/commodore-gallery/commodore-magazine-articles/commodores-approach-to-computing-pet-2001-uk-personal-computer-world-april-1978/).
**Design philosophy.** Commodore's stated aim was a full computer capability under £1,000, shifting computer purchasing from "major company board room decisions on capital equipment" to personal and departmental decisions[11](https://www.commodore.ca/commodore-gallery/commodore-magazine-articles/commodores-approach-to-computing-pet-2001-uk-personal-computer-world-april-1978/). The machine consisted of only three printed-circuit boards, the main board, the CRT board, and the cassette recorder board, designed for ease of servicing and mass production; the top of the case opened for maintenance like the hood of a car[11](https://www.commodore.ca/commodore-gallery/commodore-magazine-articles/commodores-approach-to-computing-pet-2001-uk-personal-computer-world-april-1978/) • [1](https://americanhistory.si.edu/collections/object/nmah_334374). The original 2001 integrated a cassette drive in the front of the case and used small calculator-style "chiclet" keys, which were widely criticized as poor to type on and unreliable[9](https://8bitarchitect.net/machines/commodore-pet-2001/).
## Models and specifications
The PET 2001 series was offered in 8K, 16K, and 32K configurations with an IEEE-488 bus for disk and printer communications; each system included 14K of ROM containing BASIC and a machine-language monitor, with BASIC active at power-on without loading[4](https://vintagecomputer.ca/files/Commodore/marketing/Brochure-Commodore%20PET%202001.pdf). The 2001-SN had 8K (7167 net) RAM, the 2001-16N had 16K (15359 net), and the 2001-32N had 32K (31743 net)[4](https://vintagecomputer.ca/files/Commodore/marketing/Brochure-Commodore%20PET%202001.pdf). The 8K RAM was designed to be expandable in 8K increments up to 32K, though Commodore later punched out the expansion sockets on cheaper models[11](https://www.commodore.ca/commodore-gallery/commodore-magazine-articles/commodores-approach-to-computing-pet-2001-uk-personal-computer-world-april-1978/) • [3](https://nosher.net/archives/computers/pet_brochure_1977_11_003?idx=Peddle).
The 1979 refresh, the 2001-16 and 2001-32, was the first and most significant revision: memory options of 16K or 32K, a full-size graphics keyboard replacing the chiclet keys, removal of the built-in cassette drive, and a revised operating system known as "NEW ROM" or BASIC2 that removed most of the errors in the original BASIC1[6](https://www.commodore.ca/commodore-products/commodore-pet-the-worlds-first-personal-computer/) • [9](https://8bitarchitect.net/machines/commodore-pet-2001/).
When Commodore expanded to Europe in 1978, the same machine was sold at roughly double the price with only a 220V power supply change, under the PET 3008, 3016, and 3032 (CBM 3000) badges; the 2040 dual disk drive became the 3040[6](https://www.commodore.ca/commodore-products/commodore-pet-the-worlds-first-personal-computer/). In the summer of 1980 the PET 4000 series launched in North America with the BASIC4 operating system containing built-in disk commands, in 16K and 32K memory sizes[6](https://www.commodore.ca/commodore-products/commodore-pet-the-worlds-first-personal-computer/).
**Memory technology differed across the line.** The 2001-4 shipped with 4 KB of RAM and the 2001-8 with 8 KB, both using static RAM (6550 or 2114 parts), while the later 2001-N, 3000, and 4000 machines used dynamic RAM on a different board[12](https://wiki.retrotechcollection.com/Commodore_PET_2001).
## By the numbers
Early production was limited to about thirty units per day, roughly 500 machines in the first year[1](https://americanhistory.si.edu/collections/object/nmah_334374) • [9](https://8bitarchitect.net/machines/commodore-pet-2001/). By July 1982, Commodore had sold about 242,000 systems of all types through more than 700 US dealers, shipping over 8,000 units per month[8](https://bitsavers.trailing-edge.com/pdf/datapro/datapro_reports_70s-90s/Commodore/M09-160-10_8207_Commodore_PET4001.pdf); a specialist history gives about 219,000 PET units before discontinuation in 1982[7](https://8bitarchitect.net/history/the-commodore-pet-a-wooden-box-a-six-month-deadline-and-the-machine-that-made-commodore/). The two figures measure different scopes, all Commodore systems versus the PET line.
By June 1980 the Datapro market report listed system prices of $795 for 8 KB, $995 for 16 KB, and $1,295 for 32 KB, with a typical student configuration about $900[5](https://bitsavers.trailing-edge.com/pdf/datapro/datapro_reports_70s-90s/Commodore/M09-160-10_8006_Commodore_PET.pdf).
## How it compares with the Apple II and TRS-80
The PET, the TRS-80, and the Apple II were among the first personal computers manufactured in series[13](https://hp9845.net/9845/history/comparison/). The PET 2001's package was complete in one box: 4 or 8 KB RAM upgradeable to 32 KB, Microsoft BASIC in ROM, and an IEEE-488 interface[13](https://hp9845.net/9845/history/comparison/). Its distinguishing features against its two rivals were that BASIC was active at power-on with no loading, the all-in-one case with monitor and cassette, and the IEEE-488 bus for intelligent peripherals[4](https://vintagecomputer.ca/files/Commodore/marketing/Brochure-Commodore%20PET%202001.pdf) • [11](https://www.commodore.ca/commodore-gallery/commodore-magazine-articles/commodores-approach-to-computing-pet-2001-uk-personal-computer-world-april-1978/).
In the United States, where Apple and Radio Shack held the hobbyist market, the PET never quite broke through[7](https://8bitarchitect.net/history/the-commodore-pet-a-wooden-box-a-six-month-deadline-and-the-machine-that-made-commodore/). Commodore's low-cost answer for the home was the VIC-20, released in the US in June 1980 at $299 with a color display, BASIC in ROM, and 5 KB of RAM expandable to 40 KB[14](https://www.apple2history.org/2010/10/23/the-competition-part-1/).
## Software and peripherals
The PET ran three main BASIC ROM revisions: BASIC1 (the "OLD ROM" or "ORIGINAL ROM"), which contained a number of errors; BASIC2 (the 1979 "NEW ROM"), which removed most of them; and BASIC4 (1980), which added built-in disk commands[6](https://www.commodore.ca/commodore-products/commodore-pet-the-worlds-first-personal-computer/).
The chassis allowed the attachment of two Commodore digital cassette units, an 8-bit parallel I/O device, and an IEEE-488 compatible I/O device; through the IEEE plug, up to 10 I/O devices or subsystems could be connected, with diskette storage of roughly 360 KB[5](https://bitsavers.trailing-edge.com/pdf/datapro/datapro_reports_70s-90s/Commodore/M09-160-10_8006_Commodore_PET.pdf). By the end of 1979 Commodore had filled in the biggest gaps in the product line by adding two printers, a dual diskette unit, numerous manuals, and a large selection of software[8](https://bitsavers.trailing-edge.com/pdf/datapro/datapro_reports_70s-90s/Commodore/M09-160-10_8207_Commodore_PET4001.pdf). A users' ecosystem grew alongside: Commodore ran a UK PET Users Club offering four free programs per accepted user program[11](https://www.commodore.ca/commodore-gallery/commodore-magazine-articles/commodores-approach-to-computing-pet-2001-uk-personal-computer-world-april-1978/), and over 30 PET users' groups existed by 1982[8](https://bitsavers.trailing-edge.com/pdf/datapro/datapro_reports_70s-90s/Commodore/M09-160-10_8207_Commodore_PET4001.pdf).
## PETSCII and the display
The PET's BASIC used a non-standard form of ASCII code, often called PETSCII, in which two complete character sets were available: upper and lower-case letters, and upper-case with block graphics[6](https://www.commodore.ca/commodore-products/commodore-pet-the-worlds-first-personal-computer/). Lower-case letters were reached by POKE commands switching the character set[11](https://www.commodore.ca/commodore-gallery/commodore-magazine-articles/commodores-approach-to-computing-pet-2001-uk-personal-computer-world-april-1978/). The display itself was character-only, 40 by 25 characters from 1 KB of video RAM in an 8 by 8 character cell, with no bitmap mode[12](https://wiki.retrotechcollection.com/Commodore_PET_2001); the Datapro report counted 1,000 characters per screen with 128 full-screen character graphics[5](https://bitsavers.trailing-edge.com/pdf/datapro/datapro_reports_70s-90s/Commodore/M09-160-10_8006_Commodore_PET.pdf). This combination of a graphics-rich character ROM and a character-only screen defined how PET programs drew pictures, screens, and games.
## Market reception and the end of the line
By 1982 PET sales were declining amid increased competition, and Commodore refreshed the line with the CBM-II "B" and "P" series, whose round case by Ira Velinsky won an international Industrial Design award[6](https://www.commodore.ca/commodore-products/commodore-pet-the-worlds-first-personal-computer/). The PET was discontinued in 1982[7](https://8bitarchitect.net/history/the-commodore-pet-a-wooden-box-a-six-month-deadline-and-the-machine-that-made-commodore/), with the VIC-20 and then the [Commodore 64](https://www.edgepedia.org/commodore-64) carrying Commodore's home-market push[14](https://www.apple2history.org/2010/10/23/the-competition-part-1/).
## Legacy and recent developments
The PET's architecture lived on. The VIC-20 and Commodore 64 rested on the 6502-based architecture and the same [Microsoft BASIC](https://www.edgepedia.org/microsoft-basic) license as the PET[7](https://8bitarchitect.net/history/the-commodore-pet-a-wooden-box-a-six-month-deadline-and-the-machine-that-made-commodore/), and the PET lent its architecture to those later machines, though with only 1 MHz and a maximum of 64 KB RAM, Commodore 8-bit machines could not maintain full compatibility through device drivers[15](https://dfarq.homeip.net/first-commodore-pet-sold-june-5-1977/).
**Restoration culture.** Working PETs are scarce and restoration is active. An April 2025 repair log traced a non-working PET's faults to six and a half bad chips[2](http://www.righto.com/2025/04/commodore-pet-repair.html), and in January 2026 Hackaday covered another difficult restoration of a failing PET[16](https://hackaday.com/2026/01/06/this-8-bit-commodore-pet-was-hard-to-fix/). Among the common faults are failed 6540 ROMs and 6550 RAMs, both unreliable; a 6550 with faulty enable lines can still work in the video RAM position[12](https://wiki.retrotechcollection.com/Commodore_PET_2001). Early chiclet-keyboard 2001s are scarcer and more expensive than later 4000/8000-series PETs, with keyboard and screen condition, completeness, ROM version, and early serial numbers driving price[9](https://8bitarchitect.net/machines/commodore-pet-2001/).
New hardware keeps appearing. In December 2025 a restored PET 4016 was demonstrated with an MCL65+ 6502 drop-in replacement board offering a cycle-accurate mode and accelerated modes up to the Teensy 4.1's 900 MHz[17](https://microcorelabs.com/2025/12/15/worlds-fastest-commodore-pet-using-the-mcl65-6502-drop-in-emulator/). An open-hardware CBM/PET clone can run standalone with an HDMI display and USB keyboard or serve as a mainboard replacement to repair vintage PETs, using the 6502, PIA, and VIA like the original design[18](https://github.com/DLehenbauer/commodore-pet-clone). A gate-level digital simulation of the PET 2001N-32/CBM3032 runs from a 16 MHz master clock with the 6502 at 1/16th of it (nominally 1 MHz), also covers the chiclet PET 2001-4 at an 8 MHz clock, and even reproduces the video sparkles that occur when the CPU accesses screen RAM[19](https://github.com/innot/PET-Digital-Simulation).
## References
1. [Commodore PET 2001, National Museum of American History](https://americanhistory.si.edu/collections/object/nmah_334374)
2. [A tricky Commodore PET repair: tracking down 6 1/2 bad chips, righto.com, April 2025](http://www.righto.com/2025/04/commodore-pet-repair.html)
3. [Commodore Advert, November 1977 (UK launch booklet), nosher.net](https://nosher.net/archives/computers/pet_brochure_1977_11_003?idx=Peddle)
4. [Commodore PET 2001 Series Computers brochure (manufacturer brochure)](https://vintagecomputer.ca/files/Commodore/marketing/Brochure-Commodore%20PET%202001.pdf)
5. [Datapro Report M09-160-10: Commodore PET, June 1980](https://bitsavers.trailing-edge.com/pdf/datapro/datapro_reports_70s-90s/Commodore/M09-160-10_8006_Commodore_PET.pdf)
6. [Commodore PET: The World's First Personal Computer, commodore.ca](https://www.commodore.ca/commodore-products/commodore-pet-the-worlds-first-personal-computer/)
7. [The Commodore PET: a wooden box, a six-month deadline and the machine that made Commodore, 8bit Architect](https://8bitarchitect.net/history/the-commodore-pet-a-wooden-box-a-six-month-deadline-and-the-machine-that-made-commodore/)
8. [Datapro Report M09-160-10: Commodore PET 4001 Series, July 1982](https://bitsavers.trailing-edge.com/pdf/datapro/datapro_reports_70s-90s/Commodore/M09-160-10_8207_Commodore_PET4001.pdf)
9. [Commodore PET 2001, 8bit Architect](https://8bitarchitect.net/machines/commodore-pet-2001/)
10. [A Commodore Perspective, Compute! Issue 1](https://www.atarimagazines.com/compute/issue1/3194_1_A_COMMODORE_PERSPECTIVE.php)
11. [Commodore's Approach to Computing: PET 2001, Personal Computer World, April 1978](https://www.commodore.ca/commodore-gallery/commodore-magazine-articles/commodores-approach-to-computing-pet-2001-uk-personal-computer-world-april-1978/)
12. [Commodore PET 2001, RetroTechCollection wiki](https://wiki.retrotechcollection.com/Commodore_PET_2001)
13. [Comparison HP 9845 vs. Apple II, Commodore PET 2001 and Tandy TRS-80, hp9845.net](https://hp9845.net/9845/history/comparison/)
14. [The Competition, Part 1, Apple II History](https://www.apple2history.org/2010/10/23/the-competition-part-1/)
15. [First Commodore PET sold, June 5, 1977, The Silicon Underground](https://dfarq.homeip.net/first-commodore-pet-sold-june-5-1977/)
16. [This 8-Bit Commodore PET Was Hard To Fix, Hackaday, January 2026](https://hackaday.com/2026/01/06/this-8-bit-commodore-pet-was-hard-to-fix/)
17. [World's Fastest Commodore PET using the MCL65+ 6502 drop-in emulator, MicroCore Labs, December 2025](https://microcorelabs.com/2025/12/15/worlds-fastest-commodore-pet-using-the-mcl65-6502-drop-in-emulator/)
18. [DLehenbauer/commodore-pet-clone, GitHub](https://github.com/DLehenbauer/commodore-pet-clone)
19. [innot/PET-Digital-Simulation, GitHub](https://github.com/innot/PET-Digital-Simulation)
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*Topic: Encyclopedia › Technology and the built world › Computing and digital systems › Computer hardware › Personal computers & laptops*
*Initially written Sep 17, 2026 · Reviewed: Sep 30, 2026; Oct 15, 2026 · Edited: Sep 30, 2026; Oct 15, 2026 · Last review: Oct 15, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license