Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!mailrus!umix!nancy!eecae!super.upenn.edu!rutgers!princeton!phoenix!rjchen
From: rjchen@phoenix.Princeton.EDU (Raymond Juimong Chen)
Newsgroups: comp.sys.ibm.pc
Subject: Re: 5.25 and 3.5 inch diskettes
Message-ID: <2302@phoenix.Princeton.EDU>
Date: 2 Apr 88 04:12:44 GMT
References: <976@tjalk.cs.vu.nl>
Organization: Princeton University, NJ
Lines: 25

From article <976@tjalk.cs.vu.nl>, by se6@cs.vu.nl (Houweling E):
> [suggests that there be a way to perform a DISKCOPY between different
>  media, at least from a lower density to a higher density.]

I doubt that this is possible.  Various information is kept in the
boot record, like sector size, and possibly even cluster size, and the
size of the FAT.  This information varies depending on the density
of the disk you are using.  Thus, a sector-by-sector copy is

[1] Impossible, since the sector sizes don't agree.

[2]  Possible but of dubious value, since the boot record no longer
describes the medium.  At best, you'll have a "good" disk with the
desired information, but the "extra" storage capacity will be
inaccessible.  At worst, DOS will get confused and refuse to do
anything useful with the disk.  (For example, it'll expect to see
the FAT starting at sector XX [since it thinks that it is a standard
3.5" disk] but the FAT is really stored at sector YY on 5.25" disks,
so DOS is looking in the wrong place and goes out to lunch.)

Disclaimer:  This is not gospel; just an educated guess.
-- 
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