"To take the Sideways RAM cartridges to their final design (I shouldn't say final as the RAM size can grow quite considerably)". Well I couldn't resist! I took version 3.5 and swapped out the 62256 memory for an AS6C4008 and added a hex switch to select between the sixteen pairs of banks.

This harks back to the late 80's early 90's when I designed a switched eight image EPROM and 2019 when I designed virtually the same thing as an AP6 plug in module..please see my 'Electron' and 'My Acorn Revival 2019' pages to read more about them.

PCB layout. I chose to modify v3.5 as I could fit the extra components without changing the PCB size.

Circuit Diagram.

The SRAMextreme bare board and basic components added.

The rear of the board with the hex switch socket soldered in and the front of the board with the RAM and supporting chips inserted.

The hex switch in place.

Testing banks 4, 5 and 13. Banks 4 and 5 can be switched sixteen times to load and use up to 32 ROM images - two at time!

If you would like to build one for yourself, everything you need including the Gerbers, BOM and Circuit Diagram are here - Battery Backed SRAMextreme.