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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Complete thread:

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