Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site sftig.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxn!mhuxm!sftig!rbt From: rbt@sftig.UUCP (R.Thomas) Newsgroups: net.micro Subject: Re: CD-ROMS Message-ID: <550@sftig.UUCP> Date: Tue, 16-Jul-85 14:13:05 EDT Article-I.D.: sftig.550 Posted: Tue Jul 16 14:13:05 1985 Date-Received: Thu, 18-Jul-85 04:26:25 EDT References: <11467@brl-tgr.ARPA> Organization: AT&T Bell Laboratories, Summit, NJ Lines: 35 > I would tend to doubt the practicality of "Unix on compact disks," at least > as other than a distribution medium. CD-ROM players are fairly slow in > the access time department, having a typical average seek time of 2 to > 4 seconds in most cases. The transfer rate isn't spectacular either, > but not too bad. > > ... > > The players really > aren't made for that sort of thing, and the basic parameters would > be difficult to change. > > By the way, I know of what I speak--I'm working with CD-ROMs right > now; I have an official SONY CD-ROM test disc sitting not five > feet away from me. Sounds interesting in audio players, by the way... > > --Lauren-- Not to contradict (least of all --Lauren--, whos information has always been accurate as far as I can tell) but why are the basic parameters difficult to change? The main thing that is causing the 2-4 second average seek time is the head movement time. The disks spin at several hundred rpm (I forget the exact numbers, but even 100 rpm would be only 0.3 sec average rotational latency.) The bit-rate is determined by the rotational speed, so speeding up the head positioning should not affect the external interface characteristics. As I see it, the reason CDroms are slow is that they were designed for use in audio equipment, where head movement does not need to be fast. It ought to be possible to design a fast CDrom player for computer use. And somebody will, as soon as a mass market is demonstrated to exist. At first, the fast ones will be very expensive (relative to the slow ones based on audio technology) because they will not be produced in quantity. But as they catch on, prices will come down as volumes go up. Rick Thomas ihnp4!attunix!rbt