From owner-freebsd-hackers Tue Aug 5 15:40:38 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.5/8.8.5) id PAA09903 for hackers-outgoing; Tue, 5 Aug 1997 15:40:38 -0700 (PDT) Received: from grendel.IAEhv.nl (grendel.IAEhv.nl [194.151.72.15]) by hub.freebsd.org (8.8.5/8.8.5) with ESMTP id PAA09898 for ; Tue, 5 Aug 1997 15:40:34 -0700 (PDT) Received: (from peter@localhost) by grendel.IAEhv.nl (8.8.5/8.8.5) id PAA00592; Tue, 5 Aug 1997 15:14:01 +0200 (CEST) Message-ID: <19970805151400.03327@grendel.IAEhv.nl> Date: Tue, 5 Aug 1997 15:14:01 +0200 From: Peter Korsten To: Tony Overfield Cc: hackers@FreeBSD.ORG Subject: Re: Pentium II? References: <3.0.2.32.19970803041901.006a69e4@bugs.us.dell.com> <3.0.2.32.19970804125532.0070d730@bugs.us.dell.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 0.67e In-Reply-To: <3.0.2.32.19970804125532.0070d730@bugs.us.dell.com>; from Tony Overfield on Mon, Aug 04, 1997 at 12:55:32PM -0500 Sender: owner-freebsd-hackers@FreeBSD.ORG X-Loop: FreeBSD.org Precedence: bulk Tony Overfield shared with us: > At 01:34 PM 8/3/97 -0700, Terry Lambert wrote: > > >> Don't forget than Pentium memory is 64 bits wide and 486/50 memory > >> is 32 bits wide. Thus, your fancy 486/50 memory bus cannot help to > >> explain your faster I/O claims, so maybe you've got a "magic I/O bus." > > > >Actually, PCI busses are only 32 bits wide, so the 64 bit processor > >memory path is totally irrelevent for bus master DMA speed. The > >width limitation is at the bus-to-memory interface, not at the > >processor. > > No. PCI memory writes are often posted, combined and written into > DRAM 64 bits at a time. Maybe I'm naive here, but isn't it kinda impossible to write 64 bits at one time over a 32 bits bus? 64 bits PCI isn't that wide- spread yet and while you may be able to write 64 bits at a time, they'll have to move in two chunks of 32 bits. - Peter