Simtec 340 4MB RAM expansion

The Simtec 340 4MB RAM expansion for the A300 series of Archimedes allowed users to expand their A300 machines RAM beyond the Acorn specified maximum of 1MB to the full 4MB that the MEMC controller can access.

The "340" in the name of the board is a nod to the naming convention that Acorn used when naming its machines at the time. The A305 shippeed with 512KB of RAM, the A310 shipped with 1MB of RAM, the A410, A420 and A440 shipped with 1, 2 and 4MB of RAM respectively. Therefore if Acorn had ever made an A300 series machine with 4MB of RAM it would likely have been called an Archimedes A340. 

Fitting the expansion is not as straightforward as most RAM expansions as it requires a significant amount of soldering and re-working of the original motherboard, with the removal of three integrated circuits, replacing them with turned pin sockets and also the partial removal of several resistors which are then re-connected between the original motherboard and the daughter board. 

Finally, three address lines that are not used on the A300 series RAM circuits must be connected by way of a flying lead between the new board and the MEMC chip on the motherboard.