Editing Acorn Archimedes A540 (section)

=== Motherboard Revisions ===
The A540 motherboard existed in at least two documented versions:
* Issue 1: Initial production version
* Issue 2: Revised version with minor improvements

The motherboard design utilized PAL chips to alter addressing for each MEMC, enabling the multi-MEMC memory configuration. The system used different phases of the memory clock (derived from a 72 MHz oscillator) for each MEMC, with abort signals ANDed together so an abort only occurred if all MEMCs failed to translate an address.