From: utzoo!decvax!ucbvax!C70:info-cpm
Newsgroups: fa.info-cpm
Title: CP/M Blocking and Deblocking
Article-I.D.: ucb.1422
Posted: Fri Jun 25 21:19:15 1982
Received: Mon Jun 28 06:37:11 1982

>From ucivax!csuf!bruce@Ucb-C70 Fri Jun 25 21:18:52 1982
Are there any known bugs in the sector blocking/deblocking algorithms
supplied by Digital Research with CP/M?  I don't mean the field patch that
DR distributes (the one you make to MOVCPM).  I've already installed that
one.  My problem is this:

ONLY when running the CP/M editor 'ed', files larger than one extent (128
records, in my system) end up garbled.  What happens is a sector from the
NEXT extent ends up replacing the corresponding sector in the PREVIOUS
extent.  This continues throughout the whole file.  NONE of the other
programs I have, CP/M-supplied or otherwise, do this.  I have one clue;
when I patch the BIOS to jump around the code that checks for a write to
an unallocated block, the problem goes away.  I have checked and rechecked
the code that is being skipped over, and I can't find anything wrong with
it.  The code in question is between the labels 'chkuna:' and 'alloc:'.
I'm using exactly this code in my BIOS.  Has anyone else had a problem
similar to this one?

						Bruce
						ucbvax!ucivax!csuf!bruce