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From: justin@inmet.UUCP
Newsgroups: comp.sys.ibm.pc
Subject: Re: Floppy disk access speed
Message-ID: <149000006@inmet>
Date: Wed, 4-Nov-87 09:29:00 EST
Article-I.D.: inmet.149000006
Posted: Wed Nov  4 09:29:00 1987
Date-Received: Sun, 8-Nov-87 13:14:55 EST
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Nf-From: inmet.UUCP!justin    Nov  4 09:29:00 1987


/* Written  4:33 pm  Nov  1, 1987 by john@hpcvlo.UUCP in inmet:comp.sys.ibm.pc */
<<<
< Does anyone know why floppy drive accesses are so slow?  If the disk spins
< at 300 rpms, and a track has 8 sectors, it should only take 0.0222 seconds
< to read a sector.  
----------
To read a sector from a floppy:

 Turn on motor and wait 250-500 ms for it to come up to speed
 Step to correct track at 6ms per step and then wait 15 ms for head to settle
 Issue read command and wait an average of 100 ms for sector to come around
 Read sector in next 16.384 ms

John Eaton
!hplabs!hp-pcd!john
/* End of text from inmet:comp.sys.ibm.pc */

Also, bear in mind that the sectors of a file are rarely contiguous, unless
the disk is brand-new. Thus, you have to go through the entire above procedure
for a large fraction of the sectors of the file.

				-- Justin du Coeur