Hi!
8-Янв-2005 02:21 [EMAIL PROTECTED] (Michael Devore) wrote to
freedos-user@lists.sourceforge.net:
>>MD> You'd get screen which doesn't update after EMM386 loads.
>> Ie., current EMM386 doesn't check that such maping is wrong and, thus,
>>we get hanging machine (because all subsequent "screen outputs" will
>>overwrite code, which will loaded there)?
MD> What is "wrong"?
It "wrong", because it shouldn't work (correctly) in specified
environment.
MD> If someone specifically tells EMM386 to include that range (it won't do it
MD> automatically), I pretty much figure that's what they want.
Ok. Let make another question: how to make _conditional_ inclusion of
B000 or B800 (depending of color/mono adapter(s) presence)? If I right
understand, there is currently only "not included" and "forced inclusion"?
BTW, I remember one trouble with Realtek VGA adapters: by some reason,
they sometime startup as mono adapters, thus making DOS (where was loaded
MS-EMM386 with I=b000) hanging at startup. There was hard to understand,
what happens. :( On the other side, with QEMM (without explicit I=b000!)
there was no troubles to reuse those memory areas. Now, MS-EMM386 present
HIGHSCAN option, but, as I understand, it scans memory only above F000
(or C800? - MS-HELP doesn't specify this explicitly).
MD> It's between the user and the machine at that point. Who knows, maybe
MD> the machine is reporting incorrectly and video autodetection would fail.
Yes, this may happen. Though, there is hard to fail detection, that
current video mode isn't 7 (of course, on VGA should be also examined
INT10/1A00 to check presence of second adapter).
MD> Even with a mono video in use it would, in fact, be possible to use part or
MD> all of that upper memory later on if you don't use screen I/O (or DMA it)
MD> and are careful about avoiding BIOS calls that might hit video memory.
I use I=B000 many years and up to now there was no need in making this
area unused from UMB.
MD> Perfectly plausible, although I wouldn't want to fool with it myself.
MD> What would be wrong is EMM386 refusing to map the range after the user
MD> directed EMM386 to do exactly that.
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