Date: Tue, 8 Jun 1999 09:57:35 -0400 From: "Chuck Youse" <cyouse@cybersites.com> To: "Jos Backus" <Jos.Backus@nl.origin-it.com>, "Warner Losh" <imp@harmony.village.org> Cc: "Wilko Bulte" <wilko@yedi.iaf.nl>, <zzhang@cs.binghamton.edu>, <freebsd-hackers@FreeBSD.ORG> Subject: Re: The choice of MAXPHYS Message-ID: <006001beb1b6$e16c7be0$4d7b5ccf@f8m7n1>
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I believe the DMA chip itself provides 20 bits, and external circuitry extends the remaining 4 bits. Chuck Youse Director of Systems cyouse@cybersites.com -----Original Message----- From: Warner Losh <imp@harmony.village.org> To: Jos Backus <Jos.Backus@nl.origin-it.com> Cc: Wilko Bulte <wilko@yedi.iaf.nl>; zzhang@cs.binghamton.edu <zzhang@cs.binghamton.edu>; freebsd-hackers@FreeBSD.ORG <freebsd-hackers@FreeBSD.ORG> Date: Tuesday, June 08, 1999 1:54 AM Subject: Re: The choice of MAXPHYS >In message <19990603231216.A36464@hal.mpn.cp.philips.com> Jos Backus writes: >: On Thu, Jun 03, 1999 at 07:30:20PM +0200, Wilko Bulte wrote: >: > 20 bits. But older cards can do no more than 64 kB. >: >: Indeed, 20 bits (=1 Mbyte) for the address, 16 bits for the transfer counter >: (offset). > >Isn't that 24 bits for addresses? You can dma from an ISA card to >anywhere in the first 16M... > >Warner > > >To Unsubscribe: send mail to majordomo@FreeBSD.org >with "unsubscribe freebsd-hackers" in the body of the message > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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