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From: Terry Lambert <terry@lambert.org>
Message-Id: <199604262215.PAA28075@phaeton.artisoft.com>
Subject: Re: bounce buffers
To: mrl@teleport.com (Mostyn/Annabella)
Date: Fri, 26 Apr 1996 15:15:42 -0700 (MST)
Cc: questions@freebsd.org, mrl@teleport.com
In-Reply-To: <199604260547.WAA07623@linda.teleport.com> from "Mostyn/Annabella" at Apr 25, 96 10:47:36 pm
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> > > Under what circumstances are bounce buffers indicated?
> > 
> > In a system with an ISA busmaster and more than 16M of RAM.
> 
> What about a mixed PCI ISA busmaster - e.g.
> 
> Have a system with an Adaptec 2940 UW (PCI) and an
> Adaptec 1542 (ISA).
> 
> Have the bounce on for the 1542 - what about its impact for
> everything else?

The 1542 will use the bounce buffers if the DMA source or target
is above 16M; the 2940 will never use the bounce buffers (the
driver doesn't even make the necessary calls, unles it's for the
idiot VLB cards that pretend they are EISA cards).


					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.