Hi... > >Do not ask me why CR4 TSD does not work for v86 tasks on some CPUs. > Because Intel made a mistake with it that wasn't fixed until the Pentium > Pro, and AMD slavishly followed the error?
No idea, sorry. Maybe some misunderstanding about IOPL sensitivity versus RDTSC? I would like to add that I can use RDTSC in Linux DOSEMU v86 tasks. Remember: EMM386 does not modify CR4 (at least not in any way which I have seen anywhere in the source) and STILL RDTSC, which worked in real mode and which works in DOS extenders, stops to work for the v86 task as soon as you are in EMM386. Instead of doing long research about v86 versus CR4 TSD interaction on old CPU generations I would prefer a small patch to make EMM386 emulate RDTSC. Please. Thanks! > EMM386 used to have a VCPI reserve that was 1/8th, not 1/2, of available > memory, with a maximum of 12M. So what happened? I got messages from > people complaining... Ah. Okay. 1/8th would be okay, too. Or even "EMM386 will not load, as you are trying to use a very old HIMEM. Update or specify EMM=... option to use old-compatible manual mode.". PS about RDTSC: A tight loop (12 bytes) with RDTSC inside takes 2600 cycles per round in DOSEMU, while a very similar loop with RDMSR (which already is emulated in EMM386) in plain DOS takes 300 cycles per round. Suggests that DOSEMU has to emulate RDTSC, too, so even DOSEMU has the problem that CR4 TSD does not properly affect v86 tasks (DOSEMU itself is ring 3, so CR4 TSD must be in "allow RDTSC" position, it only fails to work for v86). Eric ------------------------------------------------------- This SF.Net email is sponsored by Oracle Space Sweepstakes Want to be the first software developer in space? Enter now for the Oracle Space Sweepstakes! http://ads.osdn.com/?ad_id=7393&alloc_id=16281&op=click _______________________________________________ Freedos-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freedos-devel
