From owner-freebsd-hackers Tue Jun 8 7: 1:49 1999 Delivered-To: freebsd-hackers@freebsd.org Received: from ns1.cybersites.com (unknown [207.92.123.2]) by hub.freebsd.org (Postfix) with ESMTP id 7DF6514D6A for ; Tue, 8 Jun 1999 07:01:06 -0700 (PDT) (envelope-from cyouse@cybersites.com) Received: from f8m7n1 (dhcp77.cybersites.com [207.92.123.77]) by ns1.cybersites.com (8.9.3/8.9.3) with SMTP id IAA01728; Tue, 8 Jun 1999 08:57:48 -0400 Message-ID: <006001beb1b6$e16c7be0$4d7b5ccf@f8m7n1> From: "Chuck Youse" To: "Jos Backus" , "Warner Losh" Cc: "Wilko Bulte" , , Subject: Re: The choice of MAXPHYS Date: Tue, 8 Jun 1999 09:57:35 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 4.72.3110.1 X-MimeOLE: Produced By Microsoft MimeOLE V4.72.3110.3 Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG 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 To: Jos Backus Cc: Wilko Bulte ; zzhang@cs.binghamton.edu ; 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