Hi!
9-Дек-2004 13:36 [EMAIL PROTECTED] (Michael Devore) wrote to
[EMAIL PROTECTED]:
>>So if you can force buffering in the int21-calling software by
>>reading/writing <= 511 bytes or using an UMB or HMA transfer address but
>>not globally.
MD> Okay, stick with me on this for a bit longer. Since, as everyone seems to
MD> be saying, UMB address disk transfers are always buffered, why does EMM386
MD> need to capture DMA ports and try to do its own buffering for remapped
MD> memory when INT 13h and INT 40h are invoked?
Because INT13 may be called not only by DOS itself (for example, some
disk caching software may bypass DOS and call INT13 directly).
MD> Does anything use those two interrupts in an unbuffered state for UMB space?
LBACACHE. :)
MD> I mean, DMA-based applications would have to run a heckuva lot faster
MD> without those exceptions going off all the time when the ports are hit,
MD> unless the built-in DMA overhead swamps out exception-handling overhead.
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