FIC 486-VIP-IO ISA IOCHCK# NMI not implemented? Possible to rebuild?

Discussion about old PC hardware.

FIC 486-VIP-IO ISA IOCHCK# NMI not implemented? Possible to rebuild?

Postby ZipoBibrok » 2019-8-14 @ 15:18

Not sure if I should post this in General Old Hardware or Sound, but motherboard being the problem it probably should go here...
MPU401-emulation via AWEUTIL does not work with this motherboard. I have checked with oscilloscope that there is no activity on CPU NMI pin when IOCHCK# on ISA bus is triggered by AWE32, not even with RAM parity check enabled in BIOS. It would appear that on this board the IOCHCK# signal on ISA slots is only connected between the ISA slots and to +5V via 4.7K pull-up resistor. I cannot find a connection to VT82C486A or any of the other chips.

Does anyone have a motherboard with same chipset where the signal is connected and AWEUTIL MPU-401 emulation works? I can't find a datasheet for the chipset, but I find it hard to believe that the chipset would be so crippled to not implement it at all, so I'm hoping it only being a matter of finding the right pin and connecting it.
ZipoBibrok
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