Does that mean that all components on the MPU-401/MPU-IPC are fully understood ?

darry wrote on 2026-10-31, 06:29:

Does that mean that all components on the MPU-401/MPU-IPC are fully understood ?

Pretty much should be , this is the only custom IC on the board , the microcontroller , ram and jellybean ics are all off the shelf parts.

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.

costa wrote on Yesterday, 23:51:

wow, thank you for investing your time and money in doing that! […]
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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.

No worries i was only glad to, after seeing all the other decap projects it bothered me that no one did it for the MPU-401 so i decided to get it sent for decap my self.

Yeah hopefully someone can pull what nuked did with the mt32 and map out the logic gates.

And yeah i think the later chips just consolidated other ICs , I'm not sure if the HG series in the AT and stuff changed anything but they might have given it has some additional gates (660 usable vs 450?)

whoah this is very cool! well done.

Very nice, this looks small enough to fit into a low end CPLD ~

AppleSauce wrote on Today, 06:56:

No worries i was only glad to, after seeing all the other decap projects it bothered me that no one did it for the MPU-401 so i decided to get it sent for decap my self.

Yeah hopefully someone can pull what nuked did with the mt32 and map out the logic gates.

in that line of thoughts I have few points to add:

1) does "infosecdj " service affordable or he/she is a retro-computing-fan and voluntarily did the work for the community?
2) I don't know who and where to ask if that decap is good enough, except here:
Re: 88Emu is out (Roland SC-88/Pro/50 Emulator)

because it seems @giulio has sufficient experience.

3) based on 1) and 2) I can make a decision to sacrifice one of the two R15239182 (aka "MPU Core") chips I have in order its ROM be extracted. however, maybe better 1st idea is to put it on some prototyping ISA card like this one:

https://github.com/necroware/xt-prototyping-board

and check that ROM version is inside R15239182, because maybe it's the same ROM as on MPU-PC98II card (v1.5 found inside 6801V0B55P as well). I really don't know, R15239182 is also found on LAPC-I ISA cards and maybe someone owns such card and can say which exact MPU-401 ROM is inside R15239182 and is it the same V1.5 as in 6801V0B55P or not.