I would say that since SoftMPU exists it defeats the purpose of some mame-box emulating an mpu?

keropi wrote on 2023-10-12, 22:33:

I would say that since SoftMPU exists it defeats the purpose of some mame-box emulating an mpu?

SoftMPU has issues and limitations... in fact even simple tests show how different it responds compared to Roland ROM:

Re: Missing music in Gateway (MT-32 mode)

I would think these things got patched like they did on dosbox since then - but I can't claim to be an expert on softmpu... it is my impression that it works fine provided one meets the system reqs

keropi wrote on 2023-10-12, 22:46:

I would think these things got patched like they did on dosbox since then - but I can't claim to be an expert on softmpu...

I tested them earlier today on the latest SoftMPU v1.9 - not only they are there, but test "2A" and "1A" - cause total freeze with SoftMPU (i.e. it's worse than the old test ran on Dosbox) plus I guess MAME could be ran on the same Box where the MUNT is run, i.e. not have physically 2 boxes. basically, instead run SoftMPU on the Retro PC, run MAME on the MUNT box next to it.

I don't know which is the best way to disassemble 6801-assembler, even less I know how to read it, but even my very clumsy attempt , seems to make a lot of sense:

because MPU-401 Command 0xAC and Command 0xAD communication is the following:

Re: Roland LAPC-N / I question

and that is very obvious on the above screenshot of 6801 ASM code:

1load 0x15, compare if the CMD is 0xAC, return it

and same:

1load 0x01, compare if the CMD is 0xAD, return it

and so on. So, definitely, someone familiar with 6801-assembler can read the above better and even do some improvement to the MAME code. I guess that's also confirmation MAME ROM dump is good.

OK, here is something like a Guide and my current findings. That will save time of other people in case they want to join and help with the effort.

I am using the latest MAME 0.259 and apart of that, you need only 6 other files (that you can find and download online), you put them in sub-directory named "ct486" in your MAME roms directory:

1sha1sum roms/ct486/*
20100f8789fb4de74706ae7f9473a12ec2b9bd729 roms/ct486/1503033.bin
3b88d09be66905ed2deddc26a6f8522e7d2d6f9a8 roms/ct486/chips_1.ami
4945d405b0fb4b8f26830d495881f8587d90e5ef9 roms/ct486/et4000.bin
572134882a5c03e785db07cc54dfb7572c0a730d9 roms/ct486/natural.bin
6
700efbfb96aeb997b69bb16981c6751d3c784bb87 roms/ct486/roland__6801v0b55p__15179222.bin
8
981d2b1598c6f08bc8ea223b535025db859f51821 roms/ct486/msdos622.chd

("msdos622.chd" is optional, you can generate your own HDD image using MAME 'chdman' tool and install your own DOS or other OS, but I will not cover it, because in this case it's just waste of time)

After that running MAME with Roland MPU-401 emulation and running DOS 6.22 installation is as easy as:

mame ct486 -hard1 msdos622 -isa5 mpu401

NOTE: on the 1st run of the emulator, you need to enter the emulated 486-machine BIOS with pressing DEL and go to auto-detect the HDD and save the changes to the BIOS.

NOTE2: in case you want to exchange some files between the DOS 6.22 installation running in MAME and the "outside world" the stupidest way I found is using floppy disk image (created with WinImage) in the following way:

mame ct486 -hard1 msdos622 -flop1 f720.ima -isa5 mpu401

In order to be able to experiment and add some debug messages to Roland MPU-401 emulator you need to be able to build MAME from its source code - that turned out to be extremely easy in my 'Ubuntu 22.04.2 LTS' installation, only 3 simple steps:

1# sudo apt-get install git build-essential python3 libsdl2-dev libsdl2-ttf-dev libfontconfig-dev libpulse-dev qtbase5-dev qtbase5-dev-tools qtchooser qt5-qmake
2
3# git clone https://github.com/mamedev/mame.git
4
5# cd mame
6# make -j8

So, that initial test shows there are what seems to be minor bugs/problems with the MAME emulation of Roland MPU-401, I tracked down those problems to the time when that emulation was made - even before it was in MAME, it was initially part of the 'MESS project release 0.150' - that should explain why it's not popular, because since then (over 10 years now), no one cared to fix those small issues, here are the details:

MAME 6801-emulator seems to properly run the Roland MPU-401 ROM, but something is not quite right as the screenshot shows and explains:

I don't claim the below is the correct and the best fix - it's just way to illustrate the MAME emulation of Roland MPU-401 problems look very minor and probably easy to be ironed out:

In:
https://github.com/mamedev/mame/blob/master/s … hine/mpu401.cpp

I changed the following code:

1void mpu401_device::asic_w(offs_t offset, uint8_t data)
2{
3//  printf("MPU401: %02x to gate array @ %d\n", data, offset);
4
5	if (offset == 1)
6	{
7		m_mpudata = data;
8		m_gatearrstat &= ~STAT_RX_EMPTY;
9		write_irq(ASSERT_LINE);
10	}
11}

to:

1void mpu401_device::asic_w(offs_t offset, uint8_t data)
2{
3  printf("MPU401: %02x to gate array @ %d\n", data, offset);
4
5	m_mpudata = data;
6
7	if (offset == 1)
8	{
9		m_gatearrstat &= ~STAT_RX_EMPTY;
10		write_irq(ASSERT_LINE);
11	}
12}

and after that the result is on the screenshot below:

So, currently, my conclusion is that MAME did all the hard work - dumped the latest version of Roland MPU-401 ROM (v1.5A) and wrote 6801-emulator that is working. The communication between the 6801-Emulator and the upper layers (where DOS is running) has some issues, but they seem that should be easily fixable as I illustrated above.

[EDIT] I forgot to mention that MAME includes tools called 'unidasm' that is capable to disassemble the Roland MPU-401 ROM:

unidasm -arch m6801 roland__6801v0b55p__15179222.bin