Commodore PET
The Commodore PET is a line of personal computers produced starting in 1977 by Commodore International. A single all-in-one case combines a MOS Technology 6502 microprocessor, Commodore BASIC in read-only memory, keyboard, monochrome monitor, and, in early models, a cassette deck.
Development of the system began in 1976, and it was demonstrated and sold as the first personal computer for the masses at the January 1977 Consumer Electronics Show. The name "PET" was suggested by Andre Souson after he saw the Pet Rock in Los Gatos, and stated they were going to make the "pet computer". It was backronymed to Personal Electronic Transactor. In a 1995 retrospective, Byte magazine—and subsequently many others—referred to the PET, Apple II and TRS-80 collectively as the "1977 trinity" of pioneering personal computers.
Following the initial PET 2001, the design was updated through a series of models with more memory, better keyboard, larger screen, and other modifications. The systems were a top seller in the Canadian and United States education markets, as well as for business use in Europe.
The PET line was discontinued in 1982 after approximately 219,000 machines were sold.
History
Origins
In the 1970s, Commodore was one of many electronics companies selling calculators designed around Texas Instruments chips. TI faced increasing competition from Japanese vertically integrated companies who were using new CMOS-based processors and had a lower total cost of production. These companies began to undercut TI business, so TI responded by entering the calculator market directly in 1975. As a result, TI was selling complete calculators at lower price points than they sold just the chipset to their former customers, and the industry that had built up around it was frozen out of the market.Commodore initially responded by beginning their own attempt to form a vertically integrated calculator line as well, purchasing a vendor in California that was working on a competitive CMOS calculator chip and an LED production line.
They also went looking for a company with an existing calculator chip line, something to tide them over in the immediate term, and this led them to MOS Technology. MOS had been building calculator chips for some time, but more recently had begun to branch out into new markets with its 6502 microprocessor design, which they were trying to bring to market. Along with the 6502 came Chuck Peddle's KIM-1 design in January 1976, a small computer kit based on the 6502. At Commodore, Peddle had long dreamed of making computers and convinced Jack Tramiel that calculators were a dead-end and that Commodore should explore the burgeoning microcomputer market instead. At first, they considered purchasing an existing design, and in September 1976 Peddle asked for a demonstration of Steve Jobs and Steve Wozniak's Apple II prototype. Steve Jobs was offering to sell it to Commodore, but Commodore considered Jobs' offer too expensive.
Release
The Commodore PET was officially announced in 1976 and Jack Tramiel gave Chuck Peddle six months to have the computer ready for the January 1977 Consumer Electronics Show, with his team including John Feagans, Bill Seiler, two Japanese engineers named Fujiyama and Aoji, and Jack's son Leonard Tramiel, who helped design the PETSCII graphic characters and acted as quality control.The result was Commodore's first mass-market personal computer, the PET, the first model of which was the PET 2001. Its 6502 processor controlled the screen, keyboard, cassette tape recorders and any peripherals connected to one of the computer's several expansion ports.
The PET 2001 included either or of 8-bit RAM, and was essentially a single-board computer with discrete logic driving a small built-in monochrome monitor with character graphics, enclosed in a sheet metal case that reflected Commodore's background as a manufacturer of office equipment.
The machine also included a built-in Datasette for data storage located on the front of the case, which left little room for the keyboard. The data transfer rate to cassette tape was 1500 baud, but the data was recorded to tape twice for safety, giving an effective rate of 750 baud.
The computer's main board carried four expansion ports: extra memory, a second cassette tape recorder interface, a parallel port which could be used for sound output or connection to "user" projects or non-Commodore devices and a parallel IEEE-488 port which allowed for daisy-chaining peripherals such as disk drives and printers.
A working PET 2001 prototype was shown to the public at the Winter CES 1977 in January 1977, and the first hundred units were shipped in October, mostly going to magazines and software developers, while the machine was not generally available to consumers until December. However, the PET was back-ordered for months, so to ease deliveries, early in 1978, Commodore decided to cancel the 4 KB version.
Commodore was the first company to license Microsoft's 6502 BASIC, but the agreement nearly drove Microsoft into receivership as Commodore stipulated that they would only pay for it when the PET began shipping.
This was delayed by over six months, during which Microsoft lost money and had their cash reserves further depleted by a lawsuit over ownership of Altair BASIC. At the end of the year, Microsoft was saved by Apple's decision to license Microsoft BASIC for the Apple II line.
The BASIC included on the original PET 2001 was known as Commodore BASIC 1.0; Microsoft supplied Commodore with a source listing for their 6502 BASIC, essentially a port of BASIC-80, and Commodore performed the rest of the work themselves, including changing the startup screen and prompts, adding I/O support, the SYS command for invoking machine language programs, and fixing bugs. BASIC 1.0 still had numerous bugs and IEEE-488 support was broken, so that when Commodore later came out with disk drives, they could not be used from BASIC, and only supported 256 array elements. The PEEK function would not work on memory locations above 49152 so as to prevent the user from viewing the copyrighted code in the system ROMs.
Aside from the 8K BASIC ROM, the PET also included a 4K character ROM and an 8K kernal ROM. The first half of the kernal contained screen editor functions with the second half containing a number of function calls for tasks such as inputting and outputting data to and from different I/O devices, reading the keyboard, and positioning the cursor. In addition, the kernal ROM received system interrupts and scanned the keyboard. The kernel, an idea of John Feagans, was the first personal computer OS ROM to be a distinct entity from BASIC. The character ROM was 4K in size, containing four different 128 character tables, the uppercase/graphics character set and upper/lowercase character set, plus reverse video versions of both. This included a number of graphics characters for creating pseudographics on the screen as well as playing card symbols. On the original PET 2001, the uppercase/graphics character set and upper/lowercase character set were reversed compared to how they would be on later machines; PET owners who upgraded their machines to the BASIC 2.0 ROMs often also swapped out the character ROMs for the newer version.
Although the machine was moderately successful, there were frequent complaints about the tiny calculator-like keyboard, often referred to as a "chiclet keyboard" because the keys resembled the chewing gum it was named after. Unlike most computer keyboards, chiclet or regular, the keys on the PET's original keyboard were also squarely aligned. This was not entirely unprecedented—previously seen in the Smith Premier typewriter—but it was unusual if not uncomfortable for experienced typists. The key tops also tended to rub off easily. Reliability was fairly poor, although that was common in many early microcomputers. Because of the poor keyboard on the PET, external replacement ones quickly appeared. The PET had somewhat of a competitive advantage over its Apple II and TRS-80 rivals as both were using relatively primitive integer BASICs for their first six months on the market while the PET had a full-featured BASIC with floating-point support, a sophisticated screen editor, and lowercase letters, the last being a feature that the two competing platforms would not have for a few years. On the other hand, Commodore were a year behind Apple and Tandy in making disk drives available for their computers.
In 1979, Commodore replaced the original PET 2001 with an improved model known as the 2001-N. The new machine used a standard green-phosphor monitor in place of the white in the original 2001.
It now had a conventional, full-sized keyboard and no longer sported the built-in cassette recorder. The kernel ROM was upgraded to add support for Commodore's newly introduced disk drive line.
It was offered in 8 KB, 16 KB, or 32 KB models as the 2001-N8, 2001-N16, and 2001-N32. The 2001-N switched to using conventional DRAM instead of the 6550 SRAM in the original model. PET 2001-8Ns had eight 2108 DRAMs and 2001-16Ns used sixteen 2108s. The PET 4016 used eight 4116 chips. All 32K PETs used sixteen 4116 chips. Finally, Commodore added a machine-language monitor to the kernel ROM that could be accessed by jumping to any memory location with a BRK instruction. It did not include a built-in assembler and required the user to enter hexadecimal numbers for coding.
Commodore contacted Microsoft to upgrade BASIC for the new machines; this resulted in the soon-to-be-familiar BASIC 2.0 which removed the 256 element array limitation and had a rearranged zero page.
Most bugs were fixed and IEEE-488 support in BASIC was made to be functional. The PEEK function was unblocked for memory locations above 49152. BASIC 2.0 also included an easter egg that Bill Gates personally coded, which would cause "MICROSOFT!" to appear if the user typed WAIT 6502,x ; this was reportedly due to a dispute with Commodore over ownership of BASIC. This feature was present in all 30xx series PETs. Commodore executives were unhappy when they learned about it and it was removed from BASIC on all subsequent Commodore machines. Microsoft also remained sensitive about their copyrighted code and pressured Commodore to not release any BASIC code listings to the public, although user groups eventually made disassemblies of BASIC.
Sales of the newer machines were strong, and Commodore then introduced the models to Europe. However, Philips owned a competing trademark on the PET name, so these models were renamed. The result was the CBM 3000 series, which included the 3008, 3016 and 3032 models. Like the 2001-N-8, the 3008 was quickly dropped. Later PET 3000 series machines switched to the BASIC 4.0 ROMs.