DOS ain't dead

INT 15.87 in protected mode (Developers)

posted by Rugxulo , Usono, 01.09.2011, 05:00

> Right, which I meant CWSDPMI does not do (for whatever reason). I don't
> know how others fare, e.g. HDPMI32.

(another interesting old post from comp.os.msdos.djgpp, 02 March 1999):

>>> (John S. Fine): I never had that good an understanding of the
>>> boundaries between the extender and the DPMI server and the
>>> memory manager. If you run CWSDPMI without EMM386, then CWSDPMI
>>> is responsible for things that otherwise EMM386 would handle.
>>> I think you are saying that CWSDPMI, then uses true real mode for
>>> DOS calls, rather than using V86 mode. I think using true real mode
>>> is a bad design for many reasons, but if CWSDPMI actually works
>>> that way, then I certainly understand why having both real mode
>>> and pmode hooks for an interrupt would be needed for *best*
>>> performance.
>>>
>>> If CWSDPMI really uses real mode that way, and I was seting up a
>>> system to service 20Hz interrupts in djgpp, I think I would make
>>> sure QEMM or EMM386 or something was loaded first. Those certainly
>>> have their own overhead, but I think the problems in either servicing
>>> the interrupts in real mode, or reflecting them to pmode, would
>>> outweigh that overhead.

>> (Eli Z.): You didn't expect a 20K program written by an engineer on
>> his free time to include a memory manager and a V86 monitor, did you?

> (John S. Fine): Someday I ought to take the time to look at that
> source code (I assume it is available somewhere). It must be able
> to handle various reflections of interrupts. Having written a
> few V86 monitors myself, I would think that reflecting
> interrupts in a pmode/V86 design is enough easier than in a
> pmode/real design to cover the entire effort of the V86
> monitor (especially if V86 runs with IOPL 3, which is certianly
> no less protected than real mode).

Complete thread:

• INT 15.87 in protected mode - Laaca, 29.08.2011, 14:11 (Developers)
  • INT 15.87 in protected mode - Rugxulo, 29.08.2011, 23:28
    • INT 15.87 in protected mode - Japheth, 30.08.2011, 05:27
      • INT 15.87 in protected mode - Rugxulo, 30.08.2011, 05:37
      • INT 15.87 in protected mode - Laaca, 30.08.2011, 07:22
        • INT 15.87 in protected mode - Japheth, 30.08.2011, 08:47
          • INT 15.87 in protected mode - Rugxulo, 31.08.2011, 01:30
            • INT 15.87 in protected mode - Laaca, 31.08.2011, 07:33
              • INT 15.87 in protected mode - Rugxulo, 31.08.2011, 21:27
                • INT 15.87 in protected mode - Laaca, 02.09.2011, 07:10
                  • INT 15.87 in protected mode - marcov, 02.09.2011, 09:58
                    • INT 15.87 in protected mode - Rugxulo, 03.09.2011, 21:49
                      • INT 15.87 in protected mode - DOS386, 04.09.2011, 12:43
            • INT 15.87 in protected mode - Japheth, 31.08.2011, 10:11
              • INT 15.87 in protected mode - Rugxulo, 31.08.2011, 21:25
                • INT 15.87 in protected mode - ecm, 01.09.2011, 02:17
                  • INT 15.87 in protected mode - Rugxulo, 01.09.2011, 04:31
                    • INT 15.87 in protected mode - Rugxulo, 01.09.2011, 05:00
  • INT 15.87 in protected mode - RayeR, 07.09.2011, 10:28
    • INT 15.87 in protected mode - Laaca, 07.09.2011, 12:28
      • INT 15.87 in protected mode - RayeR, 07.09.2011, 21:05
        • INT 15.87 in protected mode - Laaca, 08.09.2011, 07:33
          • INT 15.87 in protected mode - bretjohn, 08.09.2011, 18:19
            • INT 15.87 in protected mode - Laaca, 08.09.2011, 22:39
              • INT 15.87 in protected mode - Rugxulo, 08.09.2011, 22:50
          • INT 15.87 in protected mode - RayeR, 08.09.2011, 22:27
            • INT 15.87 in protected mode - bretjohn, 09.09.2011, 00:31
              • INT 15.87 in protected mode - RayeR, 09.09.2011, 01:51
                • INT 15.87 in protected mode - bretjohn, 09.09.2011, 20:09
                • INT 15.87 in protected mode - bretjohn, 09.09.2011, 23:17