From owner-freebsd-scsi Sat Jun 8 11:00:35 1996 Return-Path: owner-freebsd-scsi Received: (from root@localhost) by freefall.freebsd.org (8.7.5/8.7.3) id LAA22025 for freebsd-scsi-outgoing; Sat, 8 Jun 1996 11:00:35 -0700 (PDT) Received: from hda (ip86-max1-fitch.zipnet.net [199.232.245.86]) by freefall.freebsd.org (8.7.5/8.7.3) with SMTP id LAA22014 for ; Sat, 8 Jun 1996 11:00:31 -0700 (PDT) Received: (from dufault@localhost) by hda (8.6.11/8.6.9) id OAA22866; Sat, 8 Jun 1996 14:05:31 -0400 From: Peter Dufault Message-Id: <199606081805.OAA22866@hda> Subject: Re: Fast SCSI-2 = 6 MB/sec ? To: petzi@zit.th-darmstadt.de (Michael Beckmann) Date: Sat, 8 Jun 1996 14:05:30 -0400 (EDT) Cc: scsi@freebsd.org In-Reply-To: from "Michael Beckmann" at Jun 8, 96 04:39:17 pm Reply-to: hdalog@zipnet.net X-Mailer: ELM [version 2.4 PL24] Content-Type: text Sender: owner-freebsd-scsi@freebsd.org X-Loop: FreeBSD.org Precedence: bulk > > I have just installed a Plextor SCSI CD ROM drive in my machine. I had to > find out that it supports only 6 MB/sec. Here is the output from dmesg: ... > I know that the CD ROM drive can never deliver a throughput of 6 MB/sec, > (actually, it should deliver around 680 kByte/sec.) but I wonder > if the CD ROM drive decreases the performance of the entire bus, thus > limiting the bus throughput to 6 MB/sec. Am I right ? Should I be > concerned about this and replace the CD drive ? No - each device will negotiate its own synchronous rate. The peak burst data rate for that CD will be 6MB, and you have to assume it will will properly disconnect and reconnect to permit effective bus utilization. -- Peter Dufault Real-Time Machine Control and Simulation HD Associates, Inc. Voice: 508 433 6936 dufault@hda.com Fax: 508 433 5267