Check the circuit around the 7809 IC.

What is the quartz crystal frequency of the color decoder in your monitor? Look around it.

Check power supply of the computer. Check 7809 stabilizer IC on the SB card.

Hi. I tried your BIOS. I couldn't guess the hotkey to enter setup though and I had to corrupt the CMOS RAM contents every time when I wanted to enter its setup. The coprocessor emulation option in setup should never be enabled because the emulation is absolute fake (you can look at the trap 7 …

The point is that the real mode software you want to run would run on a 286 AT machine flawlessly with the EMS attached. The drive is just a mere disk storage - INT13h ;) The SCSI drives were exotic back then. Hence the bugs. MFM/IDE was de facto the standard for the PC hard drives natively …

maxtherabbit, could you clone your hard drive and use an IDE drive instead?

Early 1990 AMI BIOS...Will analyze it after 10 days. Anyway your dumps are double the size that 27256 EPROMs can hold and that are shown in the picture of your motherboard. Meanwhile if you use Q87 you will solve your trap7 problem for sure and you will have a decent 387 emulation. Probably your …

Odd option, never seen it before in CMOS setup. What BIOS is that? Obviously this option when enabled made DOS4GW dos extender complain about unexpected trap 7.

Do you mean CPU writes or DMA writes to the EMS frame? How do you debug this Adaptec card of yours (sorry ,I haven't read the whole topic)?

The EMS should work with arbitrary RAM access (8,16,32,64,80 bit, etc.). It is just a RAM that is mapped to desired regions. I would recommend QEMMs Manifest (MFT) as a tool for troubleshooting OP's issue.

This option appeared in the latest 386 BIOSes like the "color" AMI BIOS. It is there on 386SX motherboards as well with the same BIOS. This option has no effect on most software that uses a x87 coprocessor. If the detection is enabled and if a real coprocessor is indeed present it only updates the …

Most motherboards don't have jumper to select the presence of a coprocessor. It is detected by means of software. A few motherboards have jumpers to select coprocessor type (i.e. weitek, 387, 287). Some motherboards have in their CMOS RAM setup option to detect or not to detect the x87 coprocessor …