Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!pasteur!agate!ig!uwmcsd1!dogie!uwvax!puff!ttang
From: ttang@puff.cs.wisc.edu (Theodore Tang)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Disk holes and other strange things (was Re: F-15 Strike Eag)
Message-ID: <1424@puff.cs.wisc.edu>
Date: 24 Feb 88 15:11:00 GMT
References: <3037@cup.portal.com> <3186@cup.portal.com> <3255@cup.portal.com> <404@mks.UUCP>
Organization: U of Wisconsin CS Dept
Lines: 26
Summary: You've contradicted yourself
	 Timeout means, timeout

In article <404@mks.UUCP>, wheels@mks.UUCP (Gerry Wheeler) writes:
> In article <1414@puff.cs.wisc.edu>,
>  ttang@puff.cs.wisc.edu (Theodore Tang) writes:
> > The ONLY time DOS uses that index hole
> > is when it formats.
> 
> Well, that is OK on a good disk, but what about a disk with a bad
> sector? I think the previous poster was right -- the disk controller
> uses the index hole as a timeout if it can't find the requested sector. 
> If you request sector 2, and the controller hasn't found sector 2 after
> seeing a couple of index pulses, it has to assume sector 2 isn't there. 
> -- 
>      Gerry Wheeler                           Phone: (519)884-2251

The keyword here is TIMEOUT.  This is exactly what DOS does, it will time,
not wait for the hole to reappear.  It doesn't have to use the hole, just know
that it take x usecs for a complete pass and if it hasn't found the desired
sector by that time, bingo!, you get a TIMEOUT.  This is kind of like when
you don't close the drive door.

Theodore Tang (Ted) @ University of Wisconsin at Madison

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