AppleSauce wrote on 2026-10-31, 06:16:
I sent it to infosecdj to get it opened up and imaged.
wow, thank you for investing your time and money in doing that!
Hitachi and Roland wrote:HD61J221F is Custom CMOS Gate Array with up to 500 Gates and 50 I/O pins in FP-54 package.
it covers almost all of Roland Intelligent MIDI devices - on top of my head the only devices not using it are MPU-401AT ISA card, MPU-IMC MCA card (for IBM PS/2) and MPU-PC98II, where Custom Gate Array in FP-64 package is used, but most likely with the same 'code' inside, only different package.
also, LAPC-I ISA cars uses R15239182 chip (aka "MPU Core"), which is highly integrated according to Roland own words:
Roland wrote:MPU Core: a hybrid IC integrating the CPU of MPU-PC98II, gate array and RAM. Its operation is fully compatible with MPU-401
or in other words it integrates the custom-gate-array from MPU-PC98II, the 6801 CPU, the SRAM and the ROM code in a single IC.
I am not an expert, but I hope the picture "infosecdj" did is good enough (and with all necessary layers removed like the metallization layer, etc) and so someone that is good in using tools like Deroute:
https://github.com/emu-russia/Deroute
or similar tool will reverse-engineer the logic gates and thus common FPGA/CPLD can be used as replacement. in any way, it's one step closer to a perfect LAPC-I replica, because current LAPC-I replica:
https://stdio.ru/index.php?n=Main.LAPC-I
is using emulated MPU-401, but everything else is original, i.e. perfect already. BTW, if that is of any interest to you - the same way you got your MPU-PC98 card, you can get "Roland D-110" (whole unit or just the main-board) and that way acquire el-cheapo all other Roland ICs to build the current LAPC-I replica card.
