Solidisk BBC
Solidisk BBC
The ATPL Sidewise board connects to the BBC B motherboard by plugging into the sockets for IC73, the 7002 ADC, and IC51, the OS ROM. The displaced chips plug into corresponding sockets on the Sidewise board, which ends up being a curious shape as a result of the location of the connecting points.
There are thirteen ROM sockets on the board, with 11 to be used for 16K ROMs and the south-easterly most two for 8K RAM chips making up a 12th "ROM", in the shape of a 16K bank of sideways RAM.
There is also provision for a battery backup to the SRAM, but it isn't fitted here.