DOS ain't dead

MSWindows 4.x DPMI doesn't like zeroed environment segment (DOSX)

posted by ecm  , Düsseldorf, Germany, 26.05.2024, 22:09

I found that MSWindows 4.x (both 95 and 98SE) doesn't like it when a DOS program in a DOS prompt window tries to enter DPMI Protected Mode with the word [PSP:2Ch] of its process holding a zero. My DPMI tests all did this to reduce their memory use. Trying to enter PM is aborted with an error like this then:

> The program encountered an invalid page exception.
>
> Fault location: 0028:C0236811
> Faulting component: DOSMGR(0E) + 00000ED5
> Interrupts in service: None

The exact 8-digit numbers differed in MSW 98SE. I think the "faulting component" had "DOSMGR(0E) + 00000EDD" there.

I reported this as well as a further problem to pcjs: https://github.com/jeffpar/pcjs/issues/75

I first noticed this earlier this weekend when dpmimini would fail while the DOS32 build of NASM entered Protected Mode without a problem.

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l

Complete thread:

• MSWindows 4.x DPMI doesn't like zeroed environment segment - ecm, 26.05.2024, 22:09 (DOSX)