OK here's the situation: I have a SCSI PCI AVA-2902I Adapter that conflicts in Memory Range C8000-CA7FF with the Bios PnP Extension. I tried Anything: You CAN'T change in the Resource Settings that range of memory in the Adapter Driver or in the Bios PnP Extension. I can only force a different IRQ Setting through CMOS but IRQ is NOT the problem. I tried all drivers, the Adaptec and Microsoft ones for my SCSI Card and nothing. The SCSI Card works perfectly in DOS, but I can't load Real Mode Drivers in Windows 98. There must be a way to assign a different Range of Memory (like CB000-CD7FF, unused), but Windows 98 doesn't allow me to do it, except for the IO Port and a different Memory Range. If I remove BIOS PnP Extension, when I reboot, Windows 98 installs it and reboots again, without asking me so. My Motherboard is an Alton VX Pro with a Pentium 166.
The ASD.log reports this is it can be useful:
Windows 98 4.10.1691
Starting a device
Adaptec AVA-2902A/E/I /AVA-2904/E /AVA-2910 PCI SCSI Controller
CI \V EN _9 00 4& DE V_ 50 78 &S UB SY S_ 00 00 00 00 &R EV _0 1\ BU S_ 00 &D EV _0 8& FU NC _0 0
So... There's a way to disable Bios PnP Extension (NO, You can't disable it for the current hardware profile), or a way to assign a different Memory Range for any of both (NO, Windows doesn't allow you to do that).
The Adapter doesn't have jumpers (to disable PnP feature) and the only thing I can do from CMOS is to change IRQ by forcing Legacy ISA. I guess the ONLY WAY to solve this is adding some undocumented parameters to the device driver.
Let's see if you can do anything...