Acorn's master plan for the BBC Micro series of computers was that they'd really just be the I/O terminals for another, much faster computer attached via a high

Acorn's master plan for the BBC Micro series of computers was that they'd really just be the I/O terminals for another, much faster computer attached via a high-speed bus; there was an RPC interface to allow the second processor unit to make system calls on the I/O computer and use its peripherals. The only second processor unit they released in bulk was a 6502 unit (3MHz with 62kB of free RAM and no interrupt overhead, so it was blisteringly fast by 8-bit standards). But there was also a Z80 unit, which would run CP/M. http://chrisacorns.computinghistory.org.uk/8bit_Upgrades/Acorn_ANC04_Z802ndproc.html http://chrisacorns.computinghistory.org.uk/8bit_Upgrades/Aco... The plan was evenutally scrapped in favour of the BBC Master, but they produced limited quantities of a 10MHz 32016 unit (running Panos) and was used to develop the original 8MHz ARM1.