Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!samsung!usc!elroy.jpl.nasa.gov!decwrl!shelby!lindy!ralerche
From: ralerche@lindy.Stanford.EDU (Robert A. Lerche)
Newsgroups: comp.lang.postscript
Subject: Re: Bitmap of PostScript code..
Summary: (re. disk speed)
Message-ID: <8167@lindy.Stanford.EDU>
Date: 22 Feb 90 05:02:30 GMT
Sender: ralerche@lindy.Stanford.EDU (Robert A. Lerche)
Reply-To: ralerche@lindy.Stanford.EDU (Robert A. Lerche)
Organization: Research Libraries Group
Lines: 16

A simple way to grok disk speed: 60 revolutions / second is the typical
hard disk speed.  So, with 17 sectors on a track (again, typical), 512
bytes/sector, we have around 500 K bytes/second (about 30 M bytes/minute)
at 1:1 interleave.

Many factors affect the actual throughput of a hard disk, like, for example,
whether the controller and host system are capable of running full speed
at 1:1 interleave.  So, using raw bitmaps it's a problem to drive a 100
page/minute marking engine.  However, with some fairly simple compression
it's probably good enough.

A historical note:  60 revs/second is the same speed that mainframe hard
disks have run at for years and years.  Some of IBM's disks run a bit faster
nowadays (I think the current 3380's go at about 80 revs/second).  The
mainframe disks have much more data per track, though, and so achieve
much higher transfer rates (up around 4 M bytes/second).