From owner-freebsd-chat Sun Sep 7 23:43:38 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.7/8.8.7) id XAA12508 for chat-outgoing; Sun, 7 Sep 1997 23:43:38 -0700 (PDT) Received: from genesis.atrad.adelaide.edu.au (genesis.atrad.adelaide.edu.au [129.127.96.120]) by hub.freebsd.org (8.8.7/8.8.7) with ESMTP id XAA12503 for ; Sun, 7 Sep 1997 23:43:33 -0700 (PDT) Received: from word.smith.net.au (lot.atrad.adelaide.edu.au [203.20.121.21]) by genesis.atrad.adelaide.edu.au (8.8.5/8.7.3) with ESMTP id QAA24655 for ; Mon, 8 Sep 1997 16:13:23 +0930 (CST) Received: from word.smith.net.au (localhost.atrad.adelaide.edu.au [127.0.0.1]) by word.smith.net.au (8.8.7/8.8.5) with ESMTP id QAA01679; Mon, 8 Sep 1997 16:00:35 +1000 (EST) Message-Id: <199709080600.QAA01679@word.smith.net.au> X-Mailer: exmh version 2.0zeta 7/24/97 To: Greg Lehey cc: Mike Smith , Simon Shapiro , FreeBSD Chat Subject: Re: lousy disk perf. under cpu load (was IDE vs SCSI) In-reply-to: Your message of "Mon, 08 Sep 1997 15:18:23 +0930." <19970908151823.35891@lemis.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Mon, 08 Sep 1997 16:00:34 +1000 From: Mike Smith Sender: owner-freebsd-chat@freebsd.org X-Loop: FreeBSD.org Precedence: bulk > >>> However, Simon is close; the ESMD spec allows for a data clock of 25MHz > >>> (the data separator is on the disk, not the controller, IIRC). > >> > >> Depends on the drive. > > > > What "depends" on the drive? > > The location of the data separator. Thinking about it, though, I'm > not sure I remember correctly. I was pretty sure we only had one read > data and one write data line, but I could have been wrong. Those > cables were about .75" thick. No, you're correct. The ESMD interface looks a lot like the ESDI interface (no surprises there, really); there's only one data line in each direction, and the separator is on the drive. > > The ESMD spec lays out the maximum clock rate for the data, and the > > separator has to be on the drive if you're going to claim to be > > ESMD. > > Well, I'm not even sure if the 3330 is ESMD. We called it SMD > (Storage Module Drive). What does the E mean? Extended? When did it > come out? IIRC, SMD maxed out at 10 or 15MHz. ESMD defined some more commands and supported increased data rates; I recall both 20 and 25MHz drives. > > I've had blood out of similar units on my hands (and blood out of my > > hands on similar units 8) and I get the distinct impression that > > multiple-head read activity was the norm. > > They may have been in the environment you're talking about. They > weren't at Tandem, and I'd guess that any multi-head stuff didn't come > until the mid-80s. Hmm. I confess that units prior to the late 70's would have been destroyed before I was old enough to understand their workings well, let alone remember them. > > Sure. I think your earlier point about the basic mechanical > > limitations is quite valid though; there's a basic restriction inherent > > in having to fling the head assembly around. Still... > > Sure. In fact, I'm astounded how much disk drives have improved in > the last 15 years. In 1982, Tandem introduced a 540 MB CDC SMD disk > drive, the disk drive for gluttons. It was a heap of shit. It Heh. I think this was the ancestor to the 515MB units that I remember so fondly. Did it make "whale noises" as part of its self-test? > that, we went to little 8" Fujitsus). Try and find a new production > disk drive *anywhere* with only 540 MB, 30 ms positioning, 800 kB/sec > transfer rate nowadays. By comparison, even the shittiest IDE drives > are a dream. Sounds like a Zip drive. 8) mike