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Date:      Tue, 01 Sep 1998 09:52:16 -0700
From:      Jason Thorpe <thorpej@nas.nasa.gov>
To:        Andrew Gallatin <gallatin@cs.duke.edu>
Cc:        mjacob@feral.com, freebsd-alpha@FreeBSD.ORG
Subject:   Re: Alpha Install - oops! 
Message-ID:  <199809011652.JAA11800@lestat.nas.nasa.gov>

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On Tue, 1 Sep 1998 12:31:48 -0400 (EDT) 
 Andrew Gallatin <gallatin@cs.duke.edu> wrote:

 > Gee, I'd hope a GL would be smart enough not to prefectch past the end
 > of a S/G segment; I do know that the page-boundry DMA restriction is gone on GL's. 
 > 
 > However, I use the direct-map segment in my Myrinet drivers (on DU &
 > on *BSD), so I can't verify that it doesn't happen.

The hardware can prefetch past the last real S/G segment.  When I implemented
S/G map DMA in NetBSD/alpha, I had to add a spill pte after the last
valid segment.

Jason R. Thorpe                                       thorpej@nas.nasa.gov
NASA Ames Research Center                            Home: +1 408 866 1912
NAS: M/S 258-5                                       Work: +1 650 604 0935
Moffett Field, CA 94035                             Pager: +1 650 940 5942

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