AMI386 and OPTi-495SX chipset

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AMI386 and OPTi-495SX chipset

Post by ppgrainbow » Sun 14 Apr, 2019 2:28 am

Hey there!

I just found out information regarding which motherboard the "AMI386 clone". The machine uses the DataExpert OPTI-495SX (471WB) motherboard.

Looking at the datasheet for the DataExpert OPTI-495SX located here: ... 495SX.html

The machine not only supports the 80386(DX) motherboard, but the 80486SX, 80486 and 80486DX2 processors.

The motherboard which relies on the OPTI-495SX chipset can only support up to 32 MB ((4) 4M x 9 SIMM on Bank 0 and (4) 4M x 9 SIMM on Bank 1). The current release of PCem supports up to 256 MB in which neither the emulated machine nor the AMIBIOS can handle.

Here is a screenshot of these embarrassing bugs that I found:
Screenshot from 2019-04-13 19-16-40.png
Screenshot displaying 256 MB of RAM that the BIOS is testing. 640 MB of RAM is the theoretical maximum that the AMIBIOS can test before the emulated machine hangs if memory beyond this limit is tested.
Screenshot from 2019-04-13 19-16-40.png (4.32 KiB) Viewed 1202 times
Screenshot from 2019-04-13 19-17-57.png
Screenshot display only 64 MB of extended RAM is usable under AMIBIOS.
Screenshot from 2019-04-13 19-17-57.png (11.92 KiB) Viewed 1201 times
If I can do this myself, I can try to pull out a fix myself. :)

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