SB16 's MPU401 IRQ \ VOGONS

SB16 's MPU401 IRQ

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First post, by Riikcakirds

Posted on 2022-11-02, 16:49

Riikcakirds Offline

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I connect my MU80 to the gameport of my Sb16 with a midi cable. The Sb16 uses dos environment values of P220 I7 D1 H5 P330 T6.
What I can't find out after searching and confused me is what is the IRQ value of the MPU401 on the SB16 gameport. Is it using IRQ7 as the MPU401 IRQ?
I ask because when I play Privateer, setup always asks for an IO address and IRQ when I select general midi for sound. It works seemingly no matter what IRQ I give it for MPU401, even IRQ 5 or 8.
I just wondered if it matters, and what is the recommended setting ( old forum posts say IRQ2/9 is most compatible for MPU401)?

Reply 1 of 4, by maxtherabbit

Posted on 2022-11-02, 18:58

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Soundblasters share the same IRQ level for both the PCM audio and MPU (a major design shortcoming)

Reply 2 of 4, by Riikcakirds

Posted on 2022-11-02, 22:40

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maxtherabbit wrote on 2022-11-02, 18:58:

Soundblasters share the same IRQ level for both the PCM audio and MPU (a major design shortcoming)

Is there any known old software/games that will not work with mpu401 if not using IRQ 2 or 9.

Reply 3 of 4, by maxtherabbit

Posted on 2022-11-02, 22:43

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Yes, but I dont have a list handy for you

Reply 4 of 4, by LSS10999

Posted on 2022-11-03, 00:43

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Riikcakirds wrote on 2022-11-02, 22:40:

maxtherabbit wrote on 2022-11-02, 18:58:

Soundblasters share the same IRQ level for both the PCM audio and MPU (a major design shortcoming)

Is there any known old software/games that will not work with mpu401 if not using IRQ 2 or 9.

IRQ 5/7 is more common for Sound Blaster (and compatible ones), but I usually use IRQ5 nowadays as I prefer leaving the LPT port as-is (378h/IRQ7) in case I need to use it in the future.

As you're using IRQ7, I think it's better if you move the LPT port to 278h/IRQ5 so the card will be the only thing taking IRQ7.

For MPU401 I'm not sure about the IRQ2/9 problem. I've tried a few games that can use MPU401 with a MIDI daughterboard, and so far they are working fine using the usual IRQ (5/7).

I had related issues with Wolf3D before. I've a CT2290 card which doesn't have jumpers for IRQ/DMA, and it defaulted to use IRQ10 and DMA3. While many other games can be configured to use that IRQ and DMA setting (or read directly from BLASTER environment variable), Wolf3D refused to run and froze on startup, unless I used DIAGNOSE to put it on standard setting (IRQ5 and DMA1).

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