I know it's not recommended as we have cheap solutions to add memory externally, but just for curiosity:
Would it be possible to e.g. replace the second bank of the 6128 by 41256 chips and drive the A8 line of these chips with a bit of additional logic? At least when someone has to replace his internal memory anyway, it might be a nice gimmick to add more internal RAM with a bit of more effort.
My idea was, to remember D3 and D4 when the PAL is addresses in a flip flop and then combine those with CAS1 and ROW to drive the A8 signal. See picture attached. Would that idea work?
Screenshot 2022-08-17 at 19.34.17.png
If yes, the Yarek 1-4MB solution probably could also work, by adding a bit more NOR logic and using a SIMM (ok, definitely ugly inside the CPC).
If the idea is not possible, I'm happy to learn. It's just an idea and I wonder if I am totally wrong with it, or if I missed something.
See German ct magazine, they did a 512 KB internal expansion for the CPC6128. 256 KB can be accessed by CRTC!
Quote from: GUNHED on 21:51, 17 August 22See German ct magazine, they did a 512 KB internal expansion for the CPC6128. 256 KB can be accessed by CRTC!
I know that one. But they replaced the PAL and the whole solution is not (fully) DK'tronics compatible. What I had in mind was to get something that is 100% compatible and behaves exactly like an external RAM extension with up to 4MB.
Yes, that would be the greatest solution. And there are already two solutions there. One is internal, works fine. the other one is the 4 MB expansion card. Works fine too. Thereads about that are somewhere in this forum.
Good luck with your solution, hope you stay compatible to the CPC6128 (dk'tronics is just a subset of it). :)