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From: rcd@ico.UUCP (Dick Dunn)
Newsgroups: comp.arch
Subject: Re: mach my day (disk head speed)
Message-ID: <1431@ico.UUCP>
Date: Mon, 24-Aug-87 14:43:41 EDT
Article-I.D.: ico.1431
Posted: Mon Aug 24 14:43:41 1987
Date-Received: Tue, 25-Aug-87 05:29:21 EDT
References: <1430@ico.UUCP>
Organization: Interactive Systems Corp, Boulder, CO
Lines: 17
Keywords: subsonic
Summary: stupid mistake corrected

Well, after I showed (correctly, I think) that the head at OD of a 14" disk
at 3600 rpm is only doing about mach 0.2, my brain disengaged and my
fingers went on to say:

> Another way to look at it:  If we can realize a bit density of, say 800 bpi
> (the effective bit density of 6250 bpi, 9-track tape) on a disk, the
> effective data rate at mach 1 is somewhat over 10 Mbit/sec.

The divide-by-8 implied there is kind of silly (also wrong!)...yes, I know
that data is not put on tape in bit-serial fashion!  Leave it at 6250 bpi
and the data rate at mach 1 (call it 1100 ft/sec) is 1100*12*6250 bits/sec
which is about 80 Mbit/sec or 10 Mbyte/sec (per surface, of course:-)

Sorry 'bout that.
-- 
Dick Dunn    {hao,nbires,cbosgd}!ico!rcd  (NOT CSNET!)   (303)449-2870
   ...Never offend with style when you can offend with substance.