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Unreal mode!

Posted: Tue Feb 10, 2004 7:03 am
by KieranFoot
Would anyone recomend using unreal mode.
As iunderstand it its real mode but with all the 32bit limits.
Am I right? So you can use real mode programming with 32bit values??? :o

Re:Unreal mode!

Posted: Tue Feb 10, 2004 9:18 am
by Pype.Clicker
unreal mode is recommended in the two following cases :
1. you're trying to extend a legacy 16-bits DOS program so that it can deal with larger datas and neither vm86, nor xms is suitable for your needs
2. you're trying to load something that will run in 32 bits mode and which is larger than 640Kb (so you cannot load it in conventionnal memory) and you don't want to bother with a disk driver called from pmode yet, and you do not wish to switch between real and protected mode for copying chunks from the conventionnal memory buffer to the high memory areas ...

basically, unreal mode consist of breaking the '64Kb' limit of real mode segments, but still keeping 16 bits instruction and segment*16+offset address formation.

Re:Unreal mode!

Posted: Wed Feb 11, 2004 5:36 am
by ASHLEY4
As i understand it you can use up to 4gb for data in unreal mode,but the code must fit in 64k.
Is that right ? .
ASHLEY4.

Re:Unreal mode!

Posted: Wed Feb 11, 2004 7:30 am
by Pype.Clicker
not exactly. The rules for the code are the same as in real mode. So you can actually have up to 640Kb of it provided that you have far call/returns ... but that usually gives programmer headaches ...

Re:Unreal mode!

Posted: Wed Feb 11, 2004 7:50 am
by bubach
not with asm.. :-)
then it?s quite hard to fill up 640 kb