Path: utzoo!utgpu!attcan!uunet!cbmvax!rutgers!mailrus!cornell!batcomputer!riley
From: riley@batcomputer.tn.cornell.edu (Daniel S. Riley)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Request to Commodore (Bad Blocks)
Keywords: trackdisk.device
Message-ID: <6392@batcomputer.tn.cornell.edu>
Date: 23 Sep 88 18:04:23 GMT
References: <8891@cup.portal.com> <5660018@hpcvca.HP.COM> <40244@linus.UUCP>
Reply-To: riley@tcgould.tn.cornell.edu (Daniel S. Riley)
Organization: Cornell Theory Center, Cornell University, Ithaca NY
Lines: 29

In article <40244@linus.UUCP> eachus@mitre-bedford.arpa (Robert I. Eachus) writes:
[somebody else wrote this, but the attribution has gotten lost.  *sigh* ]
>> * DO NOT CHANGE THE WAY YOU READ.  ONLY CHANGE THE WAY YOU WRITE. *
>>Therefore READS TAKE THE SAME AMOUNT OF TIME whether the writes are
>>decoupled from the index pulse or not.
>>We gave up track reliability for at best a 7% increase in overall
>>floppy speed.

>     Not quite, Charles, adding  track reliablity won't cost even that
>much. Right now, trackdisk.device must rewrite an entire track even if
>only  one sector is   changed, and more  important  must  read a track
>completely to write one  sector.   If a "smart" trackdisk.device knows
>where sectors  are located,  it  can do  single  sector writes  in  an
>average of 0.7 rotations,  instead of 2.2.

I was under the impression that you could not do single sector writes
without increasing the inter-sector gaps, which would mean giving up
a sector/track.  As it stands now, there is not enough space between
sectors to reliably place the heads for a single sector write.  Wasn't
the extra space part of the point of having a trackdisk.device?

Also, I would think you would want to sync reads to the index mark when
you are trying to recover sectors from a damaged track.  Otherwise, you
have to rely on ferreting out where the track starts from damaged
information, which seems a lot less reliable than knowing where on your
damaged track the sectors should be.

-dan riley (dsr@ln61.tn.cornell.edu, dsr@crnlns.bitnet)
-wilson lab, cornell u.