MOS Technology 650x microprocessor family

OSI computers based on the 6502 CPU

Ohio Scientific Industries built a range of early personal computers based on the MosTechnologies 6502 CPU.

I owned a Challenger II C2-4P computer from 1979/80 until about 1983. The 4P indicated a 4 slot back plane of which CPU & IO board used 1 sot and video card used a second slot.

Basic computer had a 1MHz 6502, 8K RAM, BASIC in 8kB of ROM, machine code monitor in 1kB ROM, 300 baud cassette interface AND a 16 colour video display with 72 characters per line x 32 lines. A sloping keyboard was also built into the front of the computer housing.

Heavily modded my C2-4P and assembled and installed a commercial 32kB memory expansion, design and built my own multifuction card with speech synthesis (using Votrax SC-01 chip and modded version of the US Navy Research Labs Text to Speech Algorithms linked into modified BASIC) plus IO which I used for a home made program cartridge port, mods to CPU board to expand ROM to 16kB to include BASIC plus, assembler, Text to Speech, Word processor (re-worked and squeezed into 2kB) and more.