The heart of the BBC was the popular 6502 processor, variants of which were also found in machines by Atari, Commodore and Apple, among many others. A summary of the architecture for the model B is as follows, along with the current status of each item in the FPGA design:

•DONE – CPU: MOS 6502 running at 2 MHz, except when accessing certain peripherals when the clock would be automatically reduced to 1 MHz.