On Mon, Jul 18, 2022 at 6:03 PM Marko Mäkelä <msmakela_at_gmail.com> wrote: > Great! Are spare 8722 MMU chips still reasonably easily available? I am Yes, I had both of them from ebay. At least one was from a seller that almost certainly sells perfectly good C128s in pieces. not too familiar with FPGAs, but I would expect that it should be > possible to create a FPGA based 8722 that would directly generate the 4 > CAS signals. Maybe it could even be done in the DIP48 footprint, by > using a suitable SMD case, say, TSOP56. Such a daughter board would also > serve as a spare part. > Having a FPGA/CPLD just to replace function of the second MMU would be an improvement already. I did some research about this. C128 PLA has been reverse-engineered to fit into a CPLD: https://github.com/jgrip/c128-verilog and someone made a commercial replacement: https://store.backbit.io/product/plaster-128/. In the same repository there is some MMU code, but it's clearly incomplete. I found a complete MMU implementation: https://github.com/eriks5/C128_MiSTer/blob/master/rtl/mmu8722.vhd but I have no idea how complex the result is. What kind of device you need to make it run. Is something like a XC9572 enough or not. Because if it is, then this person already did the work of designing a DIP48 replacement: https://github.com/Jaystonian/SOCKET-ADAPTERS/tree/master/DIP48-XC9572XL > By the way, the file gal-jed/C128_MMU256K.pdf is not in Portable > Document Format. It is some kind of obsolete output from WinCUPL: "file to be used with P-CAD Schematic Capture to generate a symbol for your device", I will remove it from repository to avoid confusion. ytmReceived on 2022-07-18 22:00:01
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