The Acorn Atom
The Acorn Atom was released in 1980 by Acorn Computers, and is the predecessor of the BBC Micro. It was based on the MOS Technology 6502 CPU, came with 2KByte of RAM that was expandable to 12K. A video RAM expansion was needed if you wanted to use the high resolution graphics. The screen memory could be upgraded to 6KByte. The machine featured an MC6847 Video Display Generator that allowed for text and graphics modes. The machine could be hooked up to a Television set or a monitor. The MC6847 was only capable of producing a 60Hz signal, which was incompatible with the European 50Hz PAL TV norm, and initially this prevented the machine from being used on many european TVs. Later Acorn produced a 50Hz PAL color card to fix this issue.
The built in BASIC version also had an assembler integrated into it, which allowed the programmer to freely use 6502 assembler in BASIC. The Atom's BASIC was developed by Sophie Wilson, and was not easy to use due to the oddities that it used compared to other popular BASIC versions. In 1982 Acorn released an upgrade board that allowed users to use the more advanced BBC Basic, that was developed for the BBC Micro.