Commodore CBM-II

The computers from Commodore from the CBM - 500 series were designed for the late 1970s. They were intended as a successor to the "PET" computer ( " Personal Electronic Transactor "). (The term " PC" / "personal computer" at that time was not yet public knowledge, he sat down from the year 1981 with the IBM - PC by. )

The computers of the series CBM 500 were equipped with 8 -bit microprocessors such as the predecessors and successors.

Within the CBM -500 series ( CBM - II series) Commodore P 500 was a model with a very futuristic design. He came from Ira Velinsky who designed, among other things also the prototype of the PET 2001 and the Atari Stacy. CBM - 500 series was an unsuccessful attempt to replace the PET / CBM series.

It was planned to build computers for Private ( P) and for business customers (B). The P model was, as later the C64, equipped with the VIC-II chip and could 16 colors and up to 320 × 200 pixel display. The B models were designed for office work and could pose with their MOS 6545 chip 25 lines of 80 characters each.

The P 500 was a computer keyboard for use with an external monitor. He was equipped with a MOS 6509 processor running at 1 MHz. This processor was able to address up to 16 banks of 64 KB by bank switching. This home computer had two joystick ports as opposed to the "B" models, the 600 and 700 series.

The P 500 is never officially went on sale. Therefore, there is in contrast to his shortly thereafter launched " brothers " of the series 600 and 700, except a sales demo any software.

Equipped with an easy to learn BASIC programming language, were the hosts of the CBM series until the early 1990s of importance, including the control of laboratory equipment and instruments, as they had an IEEE -488 interface. Even today they are still occasionally encountered.


The model numbers were assigned depending on memory allocation as follows:

  • CBM P500 (also C128 -40 or P128 or PET II) - 128 KB
  • CBM B505 - 64 KB
  • CBM B510 - 128 KB
  • CBM B520 - 256 KB