Companions of Xanth MT-32 IRQ 2 combined with SB16 issue? \ VOGONS

Companions of Xanth MT-32 IRQ 2 combined with SB16 issue?

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First post, by eddman

Posted on 2024-08-04, 19:41

eddman Offline

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Testing in 86box, when I set the game to use MT-32 for music at IRQ 2 (using the standalone MPU-401 interface, which is intelligent mode) combined with SB16 at either IRQ 5 or 7, at launch the game shows a black screen for about a minute before starting, and afterwards although there's music from the MT-32 there's no voice from the SB16.

Choosing a different available IRQ besides 2 (e.g. SB16 IRQ 7 and MT-32 IRQ 5) makes the game launch quickly and both music and voice work.

Has anyone noticed this IRQ 2 behavior on real hardware?

Reply 1 of 3, by badmojo

Posted on 2024-08-06, 01:03

badmojo Offline

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It sounds like a resource conflict - something else is using IRQ 2/9. In the BIOS on my machine I can reserve IRQs for 'legacy ISA' - IRQ 2 isn't listed so I reserve 9 (same resource) and this fixes the sort of issue you're describing.

Life? Don't talk to me about life.

Reply 2 of 3, by eddman

Posted on 2024-08-06, 18:20

eddman Offline

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I reserved IRQ 9 for ISA but it didn't help.

Reply 3 of 3, by kaebeez

Posted on 2024-08-10, 09:38

kaebeez Offline

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If it's emulating SB16 behavior correctly, the SB16 by default attempts to take over IRQ2/9 unless the MPUEN jumper is disabled. Because there's no way (as far as I know on the SB16) to change the internal MPU401's interrupt, you'd need to change the SB16 MPU401 port from 0x330 to Disabled, mimicking opening that jumper.

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