How to find errors in Protected Mode(as defined with the "1 Failure" displayed by the Landmark AT ROMs).

Emulation of old PCs, PC hardware, or PC peripherals.

How to find errors in Protected Mode(as defined with the "1 Failure" displayed by the Landmark AT ROMs).

Postby superfury » 2017-1-11 @ 11:10

I've just tried to run the Landmark AT ROM to find bugs in my emulator once again. It runs for the most part(except messing up the CGA display when it gets to the right half of the screen's tests).

334-Landmark AT ROM_UniPCemu.jpg
Landmark AT ROM result in UniPCemu's AT 80286 emulation.


Anyone knows what causes the 1 at the protected mode errors?

Edit: It does seem to display int #13 in the bottom left corner. Does that mean anything?
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Re: How to find errors in Protected Mode(as defined with the "1 Failure" displayed by the Landmark AT ROMs).

Postby vladstamate » 2017-1-11 @ 17:23

I doubt anyone knows as we do not have the source. Although I wonder if we can use some tool to disassemble the ROM. You can only guess. My suggestion is to start logging instruction from the moment they execute LMSW since that is the point they will enter protected mode and my guess is they only attempt that when they test PM stuff. Then see what is the last thing that is done in protected mode before exiting protecting (if they do that). Very likely that last thing is the failure.

Could be anything like missing a GPF or failing a CPL comparison, etc. Could be anything really.
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Re: How to find errors in Protected Mode(as defined with the "1 Failure" displayed by the Landmark AT ROMs).

Postby vladstamate » 2017-1-11 @ 17:27

Actually there is a manual for it. While it does not say much there is still something. Maybe you fail in task switching?

http://www.minuszerodegrees.net/superso ... Manual.pdf
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