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1977 - The CBM 4032 (PET)

Technical Specifications:
MOS 6502 at 1MHz
System Memory: 20K ROM - 32K RAM
User Area: 7K RAM
(10K if Basic Interpreter not used)
Qwerty keyboard
64 keys (early), 74 keys (later)
30cm Green Phosphor screen
40 columns 25 lines
256 displayable characters
192 x 200 pixels
plus low resolution (50 x 80) graphics
Piezo Tone Generator on later models
IEEE-488 Port, 8 bit parallel user port
2 x C1531 Cassette Drive ports
No joystick ports
Microsoft BASIC 1.0
Machine Language Monitor

Click on image for enlarged picture

In many ways the CBM 4032, or PET (an acronym for Personal Electronic Transactor) as it was better known, was the machine that started the whole microcomputer boom. When it was released in 1977, it set such a high standard that it's possible to regard some more recent machines as retrograde steps in comparison. With its metal case, built-in power supply, and built in monitor, the PET made its competitors of the time look shoddy. Although 8-bit, as well as 16 bit, machines had been available for at least two years before the PET was released, these were either kits or simple 'minimal systems' consisting only of chips on a printed circuit board. The PET was the first readily available microcomputer that could truly be described as 'plug-in-and-go'.

The very early versions of the PET had a built-in tape recorder with motor control, a built-in monitor, and ROM BASIC. The first PET's had a non-standard keyboard, while the later ones more closely approximated the style of a typewriter keyboard, and featured the graphics symbols on the front of the keys. It utilised the MOS 6502 microprocessor running at 1MHz and came with 32K of RAM. All that a new user had to do to was to plug it in, turn it on and almost immediately the following message would be displayed:


The PET was the only one of the early microcomputers to include the IEEE-488 parallel interface.which could address up to 15 peripherals that was used to drive both disks and printers. The IEEE-488 interface was also the standard used for interfacing to scientific laboratory equipment. Another major and unique feature of the PET was the character set. Containing both the complete ASCII set and a large variety of block graphics, these were put to some remarkably creative uses by PET owners, despite the relatively low resolution of the graphics. The heavy use of the block graphics has been reinforced by the availability of a range of printers capable of reproducing them in hard copy without the need for complex bit programming of the printer head. Of course this meant that a limited number of printers were suitable for use with the PET, and most, if not all, were Commodore products. However, a major problem of the machine, was that the codes generated by the keyboard didn't match the ASCII set, not were they arranged in any standard order.

Commodore's strong position of the ensuing years owed much to the success of the PET. Its design was essentially that of Chuck Peddle, who made three important decisions:

  1. To base the machine on the 6502 processor - the latter was made by MOS technology (a subsidiary of Commodore) and was also used by the PET's competitors in the Apple II, and the Tandy TRS-80, so Commodore had an assured supply of semiconductor components and were able to monitor their production. The birth of the PET was nevertheless problematic because Jack Tramiel (President of Commodore) insisted that the PET's memory components also derive from MOS technology, against Peddle's wishes. This led to a highly-publicised row between the two men and Peddle's abrupt departure from the company.
  2. To equip the PET with Microsoft BASIC, which meant that anyone could develop programs for the machine just by buying one.
  3. To provide a full screen editor, which made the machine much easier to use than the single-boards that microelectronics enthusiasts had been playing with since the advent of the microprocessor in the mid-1970's, and something that even the mighty IBM had not bothered to provide on their machines as standard.
The PET was a truly venerable piece of machinery, housed in its pressed steel case (in the way office furniture used to be built), it led the way for microcomputing. The price was a mere US$1295, UKŁ775 or NZ$2280 while the Datasette cost US$74.95.

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Revised: September 25, 2005.