From: utzoo!decvax!ucbvax!C70:info-cpm
Newsgroups: fa.info-cpm
Title: CP/M Blocking and Deblocking
Article-I.D.: ucb.1427
Posted: Sat Jun 26 06:24:04 1982
Received: Mon Jun 28 08:10:36 1982

>From ucivax!csuf!bruce@Ucb-C70 Sat Jun 26 06:23:53 1982
Ah HAH!!! I found the problem! It IS a bug in the Digital Research-supplied
code.  If you write the lower 128 bytes of a 256-byte UNALLOCATED blocked
sector, everything is fine.  If you then decide to read or write a sector in
another block, everything is still fine; the original unallocated sector gets
written out correctly.  However, if you then decide to write the upper 128
bytes of the altered sector, the BIOS thinks it's still in the unallocated
block, and decides not to preread the original sector.  This causes you to
lose the first 128 bytes of the sector.  After wasting an entire day on this
problem, I now have a working BIOS.  It sure would be nice if Digital Research
would send a bug fix for this problem.  It only takes one instruction to fix...

						bruce
						ucbvax!ucivax!csuf!bruce