At 09:54 AM 3/27/2004 +0200, Luchezar Georgiev wrote: >On Fri, 26 Mar 2004 13:38:50 -0600, Michael Devore wrote: > >>>UDMA requires VDS in V86 mode. Without XMS driver it can't do its tests and loads >>>but fails. >> >>HIMEM gives XMS without V86, so it theoretically should work in that situation. > >Yes, but in practice it doesn't work everywhere. What chipset (south bridge) do you >have?
It's an ALi M5229, which is an Acer Labs Aladin IV+ TX PRO if that's what you mean. I don't know a south bridge from a London bridge or a dental bridge, myself. One curious thing I noted in UDMA.ASM -- which might be perfectly valid because I know nothing about disk DMA -- is that in the DoIO routine, UDMA loads 'ah' with the BIOS timer value and then uses it as a timeout comparison on several 'in''s and 'out''s following. However, it seems to me (and as I say I could be wrong), that the timeout should be reset after each 'in' instruction or subblock, instead of cascading down through all the DoIO in's and out's with the same value. Or does timeout properly apply to the whole block of in's and out's in DoIO overall? Is it true that the 384msec worst case timeout value is based on a spec or testing, and simply increasing the timeout value won't help get rid of any DMA timed out errors? That would be too easy. >>VDS with EMM386, I didn't know how or if it would work. When I looked at the UDMA >>code, it appeared to check for a VDS flag and existence call that EMM386 would not >>have set and I thought it might work on its fallback to non-VDS mode. > >UDMA is not perfect and Jack R. Ellis abandoned it when it became clear that it can >never be made 100% compatible. He was 58 years old and became very tired of it. There >was yet another reason - I proved to be a bad "PR guy" for him :-( I wish you keep >programming when you are 58! Every programmer I know personally is closer in age to 58 than 21, so it's a phenomenon that will be more common in the coming years, I imagine. ------------------------------------------------------- This SF.Net email is sponsored by: IBM Linux Tutorials Free Linux tutorial presented by Daniel Robbins, President and CEO of GenToo technologies. Learn everything from fundamentals to system administration.http://ads.osdn.com/?ad_id=1470&alloc_id=3638&op=click _______________________________________________ Freedos-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/freedos-devel
