Acorn 6502 second processor

The BBC micro has an unusual architecture which permits the use of dual CPUs. The second CPU doesn't have to be the same as the 6502 on the main board, and various second processors were available such as the Z80, 80286 and ARM1. The purpose of the Z80 and 80286 was to run alternative software, such as CP/M and DOS. The ARM second processor was the first product to feature the ARM1 chip, and was to allow its performance to be evaluated by users.

Acorn also sold a 6502 second processor, which this is, because it provided 50% more speed and about 3 times the memory of the unexpanded BBC micro. 

The interface which allows communication between the two processors is called the Tube.

The museum's second processor is not an active exhibit, but it does work - and on special request can be hooked up to a BBC. This allows the special second processor version of Elite to be played.