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Date:      Thu, 3 Jun 1999 17:29:07 +0200
From:      Jos Backus <Jos.Backus@nl.origin-it.com>
To:        Zhihui Zhang <zzhang@cs.binghamton.edu>
Cc:        freebsd-hackers@freebsd.org
Subject:   Re: The choice of MAXPHYS
Message-ID:  <19990603172907.A20792@hal.mpn.cp.philips.com>
In-Reply-To: <Pine.GSO.3.96.990603101914.28480A-100000@sol.cs.binghamton.edu>; from Zhihui Zhang on Thu, Jun 03, 1999 at 10:40:10AM -0400
References:  <Pine.GSO.3.96.990603101914.28480A-100000@sol.cs.binghamton.edu>

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On Thu, Jun 03, 1999 at 10:40:10AM -0400, Zhihui Zhang wrote:
> The value of MAXPHYS is chosen to be 64K for the maximum raw I/O transfer
> size. I am wondering why it is not set larger.

Just a guess: maybe this has something to do with DMA address counters on ISA
cards being 16 bit? (ducks) Or is this total nonsense? :-)

-- 
Jos Backus                          _/ _/_/_/  "Reliability means never
                                   _/ _/   _/   having to say you're sorry."
                                  _/ _/_/_/             -- D. J. Bernstein
                             _/  _/ _/    _/
Jos.Backus@nl.origin-it.com  _/_/  _/_/_/      use Std::Disclaimer;


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