MPU-IMC on the MT-32 (issues with certain games)

[raymangold]

Hello,

If anyone was wondering my previous account was unrecoverable so I had to create another one (the email address it was registered to was no longer valid so I couldn't do the mandatory password reset).

I have one problem with the MPU-IMC (microchannel MPU-401). On certain games, it seems like the interface simply does not work. Two in particular are Bitmap bros. 'Gods', and Westwood's 'Legend of Kyrandia'. I recently just saw this other MPU-IMC that went up on ebay... now the curious thing is that it has an extra PCB with an IC soldered to a few pins, photo here: http://i.ebayimg.com/00/s/NzcxWDE2MDA=/z/OnYAAOSwDk5Ttnw5/$_57.JPG

I'm wondering if this extra IC provides some additional logic required for the games that are having issues. Unfortunately due to the obscurity of this particular interface I simply can't find any extensive details about it and the game compatibility problem... or any mentioning on that strange PCB that's been tacked on to the one on ebay.

Thoughts, anyone? Games like Dune 2 and Police Quest 3 work fine.

[Great Hierophant]

What model of PS/2 are you using the card in? The card is a 16-bit MCA card and I read that these cards may have trouble in faster machines or in 32-bit MCA slots. Also, neither GODS nor Kyrandia use the Intelligent MPU-401 mode, so if you had another MCA Sound Card that supports UART MPU-401, try that with the games. Third, what type of sound module are you using? Fourth, did you set up the card using the ADF file? Fifth, is your card at IRQ9? I read that it may conflict with certain devices in the PS/2 series, see here : http://ps-2.kev009.com/ohlandl/sound/Ro ... U-IMC.html

[raymangold]

The MPU-IMC has no timing issues whatsoever thankfully. The reason why some 16-bit MCA cards have trouble in faster PS/2s (like Pentiums such as my PS/2) is because they use low-speed schottkys; which if replaced with ALS or 'F' variants, resolves the problem. So typically OEMs cheapened out to use the cheaper TTL chips: in fact, these chips operate so slowly even slower MicroChannel systems can get bus timeouts!!

1st revision MT-32. The ADF is fully installed and working in its convenience partition. The card is at IRQ 5, the Sound Blaster MCV is at IRQ 7.
For fun I did set the MPU-IMC to IRQ9: what happens is that the system will halt and will need to be power cycled. It conflicts with the SCSI adapter.

The Sound Blaster MCV does have a MIDI port that I can try; I am awaiting the ALS schottky chips and the sockets to get that fixed up (and the Hakko-300, due to complications I decided to upgrade).

Thanks for the tip on both of those games being the unintelligent MPU-401 implementations... that's very curious, so it appears the intelligent games work fine for me then. Huh.

I'll report back if I can get them going through the Sound Blaster MCV MIDI port: if they do work, it would still be rather nice to know the MPU-IMC has issues with non-intelligent MPU-401 games (the MT-32 simply gets no MIDI signals). When I had it set to IRQ 9, the un-intelligent MPU-401 games would still 'call' the MPU-IMC and cause the system to hang, as well as the intelligent ones.

Cheers,

[Mau1wurf1977]

Do these games fit on a floppy? You really should test with the default IRQ 2/9 to rule out an Interrupt issue.

[raymangold]

Do these games fit on a floppy? You really should test with the default IRQ 2/9 to rule out an Interrupt issue.

The MPU-IMC does not support IRQ 2, and cannot be used on IRQ 9 due to the aforementioned conflict with SCSI (and it must be present so the system can see its 'convenience partition'):


So unfortunately I couldn't just boot off diskette to test it. However, I don't think it's an IRQ issue after asking a few friends previously.

[Great Hierophant]

Certain games will not work if you cannot use IRQ2/9, see here : https://github.com/bjt42/softmpu/wiki/C ... Mode-Games

As you are using a Pentium-type PS/2, there could be a speed issue that the CPU is too fast for the MT-32 driver.

[raymangold]

Certain games will not work if you cannot use IRQ2/9, see here : https://github.com/bjt42/softmpu/wiki/C ... Mode-Games

As you are using a Pentium-type PS/2, there could be a speed issue that the CPU is too fast for the MT-32 driver.

Hello,

Yes there are some speed issues and IRQ issues documented in certain cases-- but neither of those fit the problems the MPU-IMC is having.

I have a friend who got GODS working on his LAPC-I at IRQ 7 on a Pentium 2 (which is considerably faster than the socket 4 Pentium 1); it didn't work on the MPU-IMC at IRQ 5 or IRQ 7.

I know Legend of Kyrandia is not a picky MT-32 game either-- so the only common pattern we've got going so far is that the MPU-IMC for some reason cannot run non-intelligent games. I'm really curious as to 'why', however.

[Mau1wurf1977]

Hmm.

What about other MT-32 supporting games that don't need a intelligent mode MPU401 like Monkey Island?

[raymangold]

I tried playing Monkey Island 2 and the MPU-IMC worked fine for it (the sound setup asks for the address instead of IRQ, which I have mine at 330 of course).

I'm still in the process of getting Monkey Island 1 (the floppy version for proper MT-32 output). I will report back after I test it out.

[raymangold]

Okay after a frustrating time with the 'dial-a-pirate', I finally got the floppy version working. The MPU-IMC works with monkey island 1 just fine.

I tried GODS again, the MT-32 receives no MIDI signals from the MPU-IMC. Hmmmmm.

EDIT: Well I will be getting a 2nd revision 'head phones' MT-32 pretty soon that I'll be able to try as well, but from what Peter told me, GODS works fine on the original MT-32. At the very minimum it should be receiving a MIDI signal I would think...

[Mau1wurf1977]

Yea it doesn't matter what's connected to the MPU...

My hunch is still on the IRQ, but having said that, I have no experience with IBM computers and micro channel.

[keropi]

Regarding Gods, it's a lapc-i / cm-32l game , not a mt-32 one. Some weirdness in playback is to be expected (nothing severe as the problem described here though) with uploaded samples, they sound wrong.

[raymangold]

Regarding Gods, it's a lapc-i / cm-32l game , not a mt-32 one. Some weirdness in playback is to be expected (nothing severe as the problem described here though) with uploaded samples, they sound wrong.

Well GODS should still respond to the MPU-IMC even if it sounds incorrect with earlier devices.

I changed the MPU-IMC's address from the primary of 330 to the alternate 1330. After doing so GODS still won't work, and none of the other games that worked (like Dune 2) respond anymore; just like GODS. Is it possible that GODS uses some sort of different address instead of 330? In the ADF Roland states the application must support the address:

Code: Select all

Usually, primary address is used. To use alternate address,you need a softwear that fit it.
        Choice "Primary"   0330h-0331h int 2
        Choice "Alternate" 1330h-1331h int 2

(yes I smirk every time I see 'softwear')

After digging deeper-- when I set up the MPU-IMC as a MPU-401 compatible device under windows 95, and set the addressing accordingly: whenever windows 95 attempts to call the MPU-IMC the system freezes up and essentially becomes a potato with an IBM badge (changing the IRQ and address to something not in use causes the system NOT to hang). So it would appear the MPU-IMC does not like being told to handle MIDI commands under windows: I am not sure if this is related to the MPU-IMC not responding to specific games as per above it seems like it's an 'address' issue... I am also not sure if it is a bus timeout, or some other weirdness... I also never set up an MPU-401 interface like this on an ISA system so I am not sure if it would do the same thing.

I think the next step here may be [after all], to replace the schottky ICs from LS to ALS on the MPU-IMC if I want windows MPU-401 MIDI support. I must observe the results on the MCV Sound Blaster first. I am also still curious as to why that other MPU-IMC had an extra IC soldered in... but unfortunately I would have to buy the darn thing for examination and testing... which I don't want to as I don't need another one, heh.

Yea it doesn't matter what's connected to the MPU...

My hunch is still on the IRQ, but having said that, I have no experience with IBM computers and micro channel.

And yeah, not many people seem to use the microchannel IBMs for gaming... or any IBMs for that matter. I'm now wondering if it's actually an addressing issue: anyone can try running GODS on IRQ 5 (or 7), it will no doubt work... but if the address is changed?

[Mau1wurf1977]

I had issues with MPU-401AT and a PCI SATA card. Games such as Gateway would lock up the machine.

Question: Does your BIOS have an option for ACPI? Of so, disable it.

Is there no way you can try the system without the SCSI card?

[raymangold]

I had issues with MPU-401AT and a PCI SATA card. Games such as Gateway would lock up the machine.

Question: Does your BIOS have an option for ACPI? Of so, disable it.

Is there no way you can try the system without the SCSI card?

The computer was made in 1991, so thankfully there is no ACPI (which came out in 1996 I think). It's also hard powered much like an AT PSU (although completely proprietary with 'modular' 4 pin molex connectors).

If you absolutely think that running IRQ 9 might change something, I believe I can bypass the IML 'convenience partition' and boot into the floppy. I can try it tomorrow.

Cheers,

[raymangold]

So I finally got around to booting with diskettes and no SCSI or SCSI controller...

However, it appears GODS is coded to detect if it's being ran on A:\ and will then will refuse with: "attempt to run from non-original disk". I went ahead and edited the GODS DOS executable with a hex editor, but then it complains that there's an error with the INI config file (when there really isn't). So then it'll reinstall itself and add that line back into the executable, and the cycle repeats.

I suppose I can try contacting bitmap brothers' support, but I highly doubt I'll get a response.

Tried a few more games like master of magic, simon the sorcerer, space quest 4, they all worked fine. Master of Magic in particular was nice as you could specify every single variable. I think GODS is hard-coded to a weird address which means Kyrandia is as well. I suppose I could research some more decompilers and hex editors to see if I could just modify the game and force it to talk to IRQ 5 / 330.

EDIT:

After reviewing the PS/2 'planar' itself, it has ALS schottky chips on it too. So all MCA cards realistically should have the LS ones replace with ALS. Still waiting for the freaking hakko to arrive so I can begin this experiment...

---

So here are the current pending plans of action:
#1 see about getting that undocumented / odd MPU-IMC (I think I might just so I can do research on it, seeing as there's nothing on the internet about it).
#2 the schottky mod

I can also do other tests on the much slower Model 56. Personally, I am unconvinced I will be able to pull it off; the problem games may be hard-coded to address the PS/2 platform simply can't deal with.

[Mau1wurf1977]

Hmm that is such a shame.But I know the feeling of some games not working. Can drive you mad potentially...

[raymangold]

Well I have an update, I DID manage to get the PS/2 running the MPU-IMC on IRQ 9 (quite well actually).

However, this has not rectified kyrandia, GODS, or any others that are programmed in the same manner.

So... from what I have been able to test, it MUST be an addressing problem. They must be talking to something other than 330-- which is stupid.

[n1mr0d]

Hakko-300

One of my best investments was buying a desoldering station (ZD-985). Without it you're butchering PCB's

[Mau1wurf1977]

That's a real shame raymangold