Devices like PokeyMAX are used to resurrect old hardware in case that the piece of original hardware have failed, and it is impossible to buy a new one. I could justify that. Yet U1MB designers decided to replace a good and working base memory mapper, with their own replacement. What is even worse, their replacement is not a recreation of the original MMU chip (which logic equations are well known, as it was a PAL chip originally), but acts like a poorly written emulator - it replicates behavior of the original hardware only up to the official specs, but beyond it, behaves differently. The MMU chip actually has nothing to do with the memory expansion. It is used only for base memory (it is strange they bother to implement it as U1MB doesn't replace the base memory), and all memory extensions I know, leave it untouched. So by installing U1MB, you basically throw away good, working, original chip, and replace it with an imperfect hardware emulator. I guess it was done only for a convenient way of installing the U1MB into the MMU socket, but instead of moving the original MMU onto the U1MB board, they decided to throw it away, and recreate it in CPLD.
Moja kolekcja: Atari 1040STe (4MB), Atari 1040STfm (4MB, BLiTTER, AT-ONCE+), Atari 800XE (SIMM EXP 1MB), Atari 800XL (RAMBO XL 256kB), Atari 600XL (64kB), Sinclair ZX SPECTRUM+ (48kB), TIMEX Computer 2048 (48kB), Commodore A600 (2MB+4MB, HDD CF 4GB), Commodore C64C.