>> Why I am surprised: running on virtual machines I would have immagined >> that these would be useless. Not the least that I doubt, but I am >> *curious*, having a reasonable hardware knowledge. Could you please give >> a (short) explanation of what happens in this situation?
> I measured the speed differences, but I didn't analyze the reasons why. My > guess is that the virtualizer's BIOSes are "optimized" for reliability, not > for speed. Therefore they're doing disk I/O with PIO, but DMA is faster (and > easier?) to emulate. I was surprised first as well. I would have expected in the Int 13 BIOS some special Trap into the virtual maschine, that would simply transfer a couple of sectors, rather then read them by PIO/DMA/UDMA. For CD/DVD that's different, as the I/O is done by some driver, out of control for the BIOS writers. OTOH, they had to emulate PIO/UDMA access anyway (for Linux/Windows/etc.), so they probably took a generic BIOS (which does transfer sectors with PIO), which works as well. Given that the BIOS is usually only used to transfer a few MB during boot, the slow BIOS performance is probably not of great importance to the developers ;) Tom > ------------------------------------------------------------------------- > SF.Net email is sponsored by: > Check out the new SourceForge.net Marketplace. > It's the best place to buy or sell services for > just about anything Open Source. > http://sourceforge.net/services/buy/index.php > _______________________________________________ > Freedos-user mailing list > Freedos-user@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/freedos-user Mit freundlichen Grüßen/Kind regards Tom Ehlert +49-241-79886 ------------------------------------------------------------------------- SF.Net email is sponsored by: Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://ad.doubleclick.net/clk;164216239;13503038;w?http://sf.net/marketplace _______________________________________________ Freedos-user mailing list Freedos-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-user
