Commodore PET

The PET (Personal Electronic Transactor) was a home-/personal computer produced by Commodore starting in the late 1970s. Although it was no top seller outside the US and UK educational market, it was Commodore's first computer and would form the basis for their future success.

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Table of contents

1 History 1.1 Origins and the early models 1.2 Education, business, and computer science 1.3 The graphics issue 2 Model Summary 2.4 PET 2001 series / 2001-N & -B series, CBM 3000 series 2.5 PET 4000 series / CBM 8000 series 2.6 SuperPET 9000 series 3 PET Trivia 4 External Links

History

Origins and the early models

In the 1970s Texas Instruments was the main supplier of CPUs for use in calculators. Many companies sold calculator designs based on their chip sets, including Commodore. However, in 1975 TI increased the price to the point where the chip set alone cost more than what TI sold their entire calculators for, and the industry they had built up was frozen out of the market.

Commodore responded by looking for a chip set of their own they could purchase outright, and quickly found MOS Technologies who were bringing their 6502 design to market. Along with the company came Chuck Peddle's KIM-1 design, a small computer kit based on the 6502. At Commodore, Peddle convinced Jack Tramiel that calculators were a dead-end. Instead they should focus on making a "real" machine out of the KIM-1, and selling that for much higher profits.

The result was the first all-in-one home computer, the PET. The first model was the PET 2001, including either 4KB (the 2001-4) or 8KB (2001-8) of RAM. It was essentially the KIM-1 with a new display chip (the MOS 6545) driving a small built-in black-and-white monitor with 40x25 character graphics. The machine also included a built-in Datassette for data storage located on the front of the case, which left little room for the keyboard. The 2001 was announced in 1977 and started deliveries around September. However they remained back-ordered for months, and to ease deliveries they eventually cancelled the 4K version early the next year.

Although the machine was fairly successful, almost everyone complained about the tiny keyboard. This was addressed in upgraded "dash N" and "dash B" versions of the 2001, which put the cassette outside the case, and included a much larger and better feeling keyboard. Internally a newer and simpler motherboard was used, along with an upgrade in memory to 8K, 16K or 32K, known as the 2001-N-8, 2001-N-16 or 2001-N-32, respectively.

Sales of the newer machines was strong, and Commodore then introduced the models to Europe. However there was already a machine called PET for sale in Europe from the huge Dutch Philips company, and the name had to be changed. The result was the CBM 3000 series ('CBM' standing for Commodore Business Machines), which included the 3008, 3016 and 3032 models. Like the 2001-N-8, the 3008 was quickly dropped.

PET/CBM Model 4032

Add-on: Disk drives

Education, business, and computer science

The final version of what could be thought of as the "classic" PET was the PET 4000 series. This was essentially the later model 2000 series, but with a larger black-and-green monitor and a newer version of Commodore's BASIC programming language. By this point Commodore had noticed that many customers were buying the "low memory" versions of the machines and installing their own RAM chips, so the 4008 and 4016 had the sockets punched out of the motherboard.

The 4032 was a huge success in schools, where its tough all-metal construction and all-in-one design made it better able to stand up to the rigors of classroom use. Just as important in this role was the otherwise underutilized IEEE 488 port the PET included. Used wisely, the port could be used as a simple "network" and allowed printers and disk drives (at this point in time, very expensive devices) to be shared among all of the machines in the classroom.

Two more machines were released in the PET series. The CBM 8000 included a new display chip which drove a 80x25 character screen, but this resulted in a number of software incompatibilities with programs designed for the 40 column screen, and it appears to have not been popular as a result. The machine shipped with 32K standard as the 8032, but allowed another 64K to be added externally. Later the upgrade was installed from the factory, creating the 8096. Later models used an improved case with a separate keyboard and swivel mount for the monitor, known as the SK's and Execudesk.

The last in the series was the SP9000, known as the SuperPET or MicroMainframe. This machine was designed at the University of Waterloo for teaching programming. In addition to the basic CBM 8000 hardware, the 9000 added a second CPU in the form of the Motorola 6809 and included a number of programming languages including BASIC in ROM for the 6502 and APL, COBOL, FORTRAN, Pascal and a 6809 assembler on floppies for the 6809. It also included a terminal program which allowed the machine to be used as a "smart terminal" as well, so this single machine could replace many of the boxes currently in use at the university. Additionally this machine became a remote development environment where the user could later upload their creation to a mainframe after completing development and testing on the SuperPET.

The graphics issue

As a home computer the line was quickly surpassed in sales by machines that included color graphics and sound, mainly the Apple II, Atari 8-bit family and TRS-80. Although color was later solved in the Commodore VIC-20 and Commodore 64, the graphics issue could have been much less annoying if not for one problem -- the character set was "hard wired" in ROM, meaning it could not be changed. On other machines the location of the character graphics could be changed and pointed to RAM, where new characters could be drawn to create graphics. On the upside the PETs used a fairly good set of graphics characters (in their extended ASCII, known as PETSCII) which allowed some rudimentary games to be created.

Model Summary

PET 2001 series / 2001-N & -B series, CBM 3000 series

CPU: MOS 6502, 1MHz

RAM: 4K, 8K, or 16K / 8K, 16K, or 32K

ROM: 18K, including BASIC 1.0 / 20K, including BASIC 2.0 (most CBM's with 3.0)

Video: MOS 6545, 9" monochrome monitor, 40×25 character display

Sound: none / single piezo "beeper"

Ports: MOS 6520 PIA, MOS 6522 VIA, 2 Datassette (1 used / 1 on the back), 1 IEEE-488

Notes: 69 key chicklet keyboard and built-in Datassette / full-sized, full-travel keyboard, no built-in Datassette

• Seventeen years old at the time, British videogame designer-to-be Jeff Minter taught himself 6502 machine code on his school's PET 2001-8. At twenty Minter founded his own company (still in operation as of 2003), using his PET-obtained skills to develop games on his newly acquired VIC-20, getting his commercial breakthrough with the classic Gridrunner. Later Minter went on to write entertainment software for the C64 as well as many non-Commodore platforms.

• http://www.zimmers.net/cbmpics/