After probably more than a year, I've fired up my 386/486DLC box to update it and start using it again. One thing I did was move over the GUS card from my Asus PVI-486 SP3 into this one (that faster system has an AWE32 and NEC XR385 to suit its 'later' status).

The specs are:

FIC 386SC
Ti 486DLC-40
256kb cache
8x 1MB 60ns
Rio444 PS2 Mouse card (COM1 03E8h)
CL-GD5428
3C509B (flashed to use bae 310, IRQ 11)
SB16 CT2290 (SET BLASTER=A220 I7 D1 H5 T5 P300)
GUS MAX v1.8 (SET ULTRASND=A240,3,3,5,5) (no megaem, ultramid etc loaded)
Roland MPU-IPC-T (default jumpers; 330 & IRQ2)

With the GUS in place, nothing will detect an MPU401 at 330. The standard Creative MPU port at 300 is detected (MPUEN is closed, and MPUSEL is open), but I have nothing connected to it of course.
With the GUS removed, everything starts working through the Roland card at 330 again (I have a 5.25" bay mounted MT32Pi install) and the synth springs into life.

The GUS is not seemingly configured to use any resources that clash with the Roland card, but it stops it working every time it is plugged back in again.

Tested with blank config/autoexec setups, with stock 8MHz ISA clock speeds. The end result it the same - plug the GUS in, and the Roland card stops working.

I cannot see a MPU jumper on the GUS, is there a software disable feature? I've tried using diagnose.exe and ultrinit.exe for the SB and GUS respectively, I've tried using unisound.exe for one or both (it never seems to initialise the GUS). Both sound cards work perfectly when configured (i.e in Duke3d sound setup all of the possible combinations of SB+GUS work simultaneously without issue).