A Guide to Commodore PETs

December 18, 2024

The original line-up of Commodore PET computers at a glance.

While the Commodore PET is quite easily and unmistakably identified by its unique form factor, the basic model evolved quite a bit over the years. Here’s a comprehensive guide to the various models of the original line-up (not including the later 82xx / SK / CBM-II or “B” series with rounded case and separate keyboard) and their basic features:

PET 2001 (original) — 1977

9" screen (white or green phosphor) @ 60 Hz
40 cols × 25 rows
static RAM (SRAM)
discrete TTL video circuitry
slow SRAM video memory with 1 MHz access time, conflicts with CPU memory access, causing “snow” when video memory is accessed during the visible portion of the video signal.
BASIC outputs to screen during V-BLANK only.
– BASIC 1 (buggy, marginal disk/IEEE-488 support, no built-in memory monitor, PEEK returns 0 for ROM addresses)
– BASIC 2 (upgrade and later production models, also known as “BASIC 3”)
16K ROM, no extra ROM slots (as required for BASIC 4.0 or option ROMs)
4K or 8K of RAM, up to 32K externally
built-in cassette drive + port for 2^nd drive
chiclet keyboard (graphics layout, Japanese variant with Katakana)
black or blue monitor bezel and/or badge
no sound, external CB/sound via user port

Since 1978 the PET 2001 was also rebadged as “CBM 3001 Series” (still type-labeled as 2001, as in “2001-32”) or “CBM 2001 Series” in Canada and Europe to avoid trademark conflicts with Philips / Softlab Munich in these markets. 8K of RAM; also 16K and 32K, probably with a newer main board revision (see below), but still featuring the same externals with cassette drive and chiclet keyboard.

PET 2001-N / CBM 30xx (“/B” with business keyboard) — 1979

9" screen @ 60 Hz
40 cols × 25 rows
dynamic RAM (DRAM), no “snow”
discrete TTL video circuitry
— BASIC 2 or
— BASIC 4.0 with additional disk commands (also available as upgrade)
BASIC 4.0 screen output doesn’t wait for V-BLANK anymore.
additional ROM slots for up to 30K total
8K, 16K or 32K of RAM
no built-in cassette drive, 1 external port (+ 1 internal)
full-travel keyboard, graphics (N) or business (B) layout

PET/CBM 40xx (early) “Thin 40” — 1980

9" screen @ 60 Hz
40 cols × 25 rows
“dynamic board” (similar to PET 2001-N), no “snow”
discrete TTL video circuitry
BASIC 4.0 (runs all versions of 40-column ROMs)
4K, 8K, 16K or 32K of RAM
external cassette port (+ 1 internal)
full-travel graphics (N) or business (B) keyboard

PET/CBM 80xx (early) — 1980

12" screen @ 50/60 Hz
80 cols × 25 rows, pixels vertically duplicated
“80-column board” with dynamic RAM, no “snow”
CRTC video chip
BASIC 4.0 (runs only 80-column BASIC 4.0 ROMs)
8K, 16K or 32K of RAM
external cassette port (+ 1 internal)
full-travel business keyboard
built-in piezo speaker

PET/CBM 40xx “Fat 40” and 80xx (late) — 1981

12" screen @ 50/60 Hz
– 40xx: 40 cols × 25 rows (1K video RAM)
– 80xx: 80 cols × 25 rows, pixels vertically duplicated (2K)
“universal board” for all models
CRTC video chip
BASIC 4.0
16K or 32K of RAM
external cassette port (+ 1 internal)
full-travel keyboard, graphics or business (80xx)
built-in piezo speaker

SuperPET SP9000 — 1981

12" screen
80 cols × 25 rows, pixels vertically duplicated
dual CPU: MOS 6502 and Motorola 6809
additional Mode / CPU switches
“universal board” with daughter boards
CRTC video chip
BASIC 4.0 for MOS 6502
Waterloo BASIC, APL, COBOL, FORTRAN, PASCAL for Motorola 6809
96K of RAM
extended character ROM with support for APL characters
external cassette port (+ 1 internal)
full-travel keyboard
built-in piezo speaker

Disclaimer: information provided with no guarantee of correctness or completeness, use at own risk. This is just an informational overview compiled from various scources.

The PET 2001 online emulator covers the original PET 2001, the PET 2001-N and the PET 2001/B (and their synonymous equivalents).

And that’s it, for today.

Norbert Landsteiner,
Vienna, 2024-12-18