Xref: utzoo comp.unix.wizards:6079 comp.arch:3121
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From: norman@a.cs.okstate.edu (Norman Graham)
Newsgroups: comp.unix.wizards,comp.arch
Subject: Re: CD-ROM speed
Message-ID: <3058@okstate.UUCP>
Date: 13 Jan 88 04:26:32 GMT
References: <4603@ihlpg.ATT.COM>
Organization: Oklahoma State Univ., Stillwater
Lines: 30

in article <4603@ihlpg.ATT.COM>, tainter@ihlpg.ATT.COM (Tainter) says:
> What makes them slow is seek times.  Optical disks give you very
> dense packing of tracks, this means you need very fine advances, which means
> careful movement, which means slow [...]

We must remember that a track on a CD-ROM is very different than a track
on a conventional magnetic hard disk. Tracks may be different sizes on the
same disk (there may even only be one track for the whole disk (or maybe
there has to be two, I don't remember)).  What makes CD-ROM slow is that
even if you know the minute, second, and sector of the data that you
want, all the drive can do is get close to where it thinks it might
be and start streamming off data until it gets to what you wanted.

> Also, what is to say we can't remork CD roms with alternative servos?

We could, but it would defeat one advantage of CD-ROM drives... they're
cheap (or at least they will be by the 2nd quarter of this year :-).
Since to make a CD-ROM drive you take a CD-Audio drive (which has a HUGE
market as compared to CD-ROM), take out a lot of electronics, and put a 
little bit of electronics back in, CD-ROM drives should approach the
price of CD-Audio drives (< $200 US).

> --j.a.tainter

--
Norman Graham
Oklahoma State University              Internet:  norman@a.cs.okstate.edu
Computing and Information Sciences         UUCP:  {cbosgd, ihnp4,
219 Mathematical Sciences Building                 rutgers}!okstate!norman
Stillwater, OK  74078-0599