VIC-20

computer A home computer made by Commodore with a 6502

CPU, similar in style to the Commodore 64 and CommodoreC16. The VIC-20 was released before the C64, and after the

Commodore PET(?). It was intended to be more of a low-end

home computer than the PET.

The VIC-20 had connectors for game cartridges and a tapedrive (compatible with a C64). It came with five kilobytes

of RAM, but 1.5 KB were used by the system for various

things, like the video display (which had an unusual 22x20

char/line screen layout), and other dynamic aspects of the

operating system (such as it was). The RAM was expandable

with a plug-in cartridge which used the same expansion port as

games. Port expander boxes were available to allow more than

one cartridge to be connected at a time.

RAM cartridges were available in several sizes: 3K, 8K, 16K

and 32K. The internal memory map was re-organised with the

addition of each size cartridge, leading to the situation that

some programs would only work if the right amount of memory

was available. The 32K cartridges were all third-party and

had switches to allow the RAM to be enabled in sections so

that any expansion size could be achieved.

BASIC programs could use at most 24 KB of RAM. Any extra

occupied the location usually used by ROM cartridges

(i.e. games). This allowed people to copy ROM cartridges to

tape and distribute them to their friends, who could load the

tape into the top 8k of their 32k RAM packs.

The name "VIC" came from the Video Interface Chip that was

also used in the other, later, Commodore 8-bit computers.

(2000-03-28)