If the ACID isn't matched to the program on the ROM (which it doesn't seem to be, otherwise this device wouldn't work) then it shouldn't be that difficult to reverse engineer the ACID chip and replace it with a low-cost PIC. Unfortunately I have neither a CPC Plus nor a GX4000 nor a cartridge, but if I happen to acquire them at some time, I might make this my next project. Bryce
ACID is not matched. "shoudn't be that difficult to reverse engineer the ACID chip". Sorry, it is more complex than you think, the ACID and ASIC talk to each other all the time and if the ACID doesn't reply, the ASIC blocks read access to ram. already the Spanish forum found this. It somehow blocks the read of any ram from z80 if it isn't copied 100%. But if you can help, please visit the forum and post there. Arnoldemu