The main problem is addressing. If there are no address lines, that leads to piggy-backs to connect the CPU to the chip selects on the memory chips. In this case, there are a second set of pads on the back of the board. Decoupling caps and pull-ups are already in place, all you need to do is add chips, giving 16 Mb. This means that the Mk1 can keep pace with larger databases resulting from newer, bigger disks.

Putting chips with a larger address range in place of the originals was possible, but the majority of the chips that could have been used are now obsolete and unavailable. Even the original memory chips are in short supply.

As soon as I can source a supply I'll be trying this out on my own player (# 15, if this makes you think about how seriously I am taking this) and I'll let you know more.