Acorn Computers is best known for the BBC computer in the 1980s and the ARM cpu architecture (you will own several of these, whether you know it or not...). The ATOM was a predecessor of the BBC computer (which started life under the name Proton).
This was my first computer.
Date: 1979
CPU: 6502 @ 1 MHz
RAM: 12 KB
Disk: optional 100 KB floppy drive