Date: Thu, 3 Jun 1999 19:30:20 +0200 (CEST) From: Wilko Bulte <wilko@yedi.iaf.nl> To: Jos.Backus@nl.origin-it.com Cc: zzhang@cs.binghamton.edu, freebsd-hackers@FreeBSD.ORG Subject: Re: The choice of MAXPHYS Message-ID: <199906031730.TAA00686@yedi.iaf.nl> In-Reply-To: <19990603172907.A20792@hal.mpn.cp.philips.com> from Jos Backus at "Jun 3, 1999 5:29: 7 pm"
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As Jos Backus wrote ... > 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? :-) 20 bits. But older cards can do no more than 64 kB. What would be nice to have is some kind of interface so that the card driver can tell the higher layers what it's capabilities are in this respect. | / o / / _ Arnhem, The Netherlands - Powered by FreeBSD - |/|/ / / /( (_) Bulte WWW : http://www.tcja.nl http://www.freebsd.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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