Editing Acorn Archimedes A500 (section)

== History ==

The A500s first ran with an ARM1 and were upgraded to the ARM2, which added the multiply instruction, while they were in use.<ref name="chris" /><ref name="chrisarc">Whytehead, Chris. [https://chrisacorns.computinghistory.org.uk/Computers/Archimedes.html "Archimedes"], Chris's Acorns (retrieved 2026-10-02). The A500 was the development machine for the whole Archimedes family; it first used the ARM1 and was later upgraded to the ARM2.</ref> Paul Fellows recalled that the machines were at first connected to BBC Micros by an umbilical into the Tube port, with the BBC doing all the input and output. The video, keyboard and filing systems were moved across to the A500 one at a time, until the umbilical was removed and the machine started on its own at the BASIC prompt: "Arthur was born!"<ref name="chris" /> A separate A500 second processor board, which used a BBC Micro in the same way, also survives; Chris Whytehead has one and lists a working example as wanted.<ref name="sp">Whytehead, Chris. [https://chrisacorns.computinghistory.org.uk/8bit_Upgrades/Acorn_A5002ndProc.html "Acorn A500 second processor"], Chris's Acorns (retrieved 2026-10-02). Board SKB 0000 022A, stripped of most chips; sockets for the ARM, MEMC, IOC and VIDC; Tube interface; circuit diagram.</ref>

Chris Whytehead's second A500, serial number 104, has a board label dated 3 March 1987, so more A500s were built after the first 100. He has also seen an Issue C board in serial number 222.<ref name="chris" />