*BSD News Article 6422


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Newsgroups: comp.unix.bsd
Path: sserve!manuel.anu.edu.au!munnari.oz.au!spool.mu.edu!sdd.hp.com!zaphod.mps.ohio-state.edu!cs.utexas.edu!uunet!mcsun!sun4nl!star.cs.vu.nl!versto
From: versto@cs.vu.nl (C Verstoep)
Subject: Weird Problem (50 MHz, SCSI)
Message-ID: <Bw227w.6Bw@cs.vu.nl>
Summary: new files sometimes show a few corrupted bytes on my system
Keywords: SCSI, file corruption
Sender: news@cs.vu.nl
Organization: Fac. Wiskunde & Informatica, VU, Amsterdam
Date: Tue, 13 Oct 1992 10:23:55 GMT
Lines: 41

Hi,

The last couple of days I have (as of now unsuccessfully) tried to install
386BSD0.1 on my new system.

My setup is as follows:
	- 50 Mhz local bus UMC mother board
	- 16 Mb memory, 70ns SIMMs
	- Adaptec 1542B scsi controller
	- Fujitsu 2624F 520 Mb scsi disk.

The problem is that newly created files sometimes have a few corrupted bytes.
It often happens when reading in the bin01.* floppies (40% of the files
will typically cause "extract" to complain).  I can also reproduce it
by just using the hard disk, so the floppy drive is not the problem.

When it happens, the file corruption is always of a fixed pattern:
7 or 8 alternate bytes somewhere in the file are replaced by a certain (fixed)
"error pattern".  I found this out by means of the following test:

- Create increasingly large text files consisting of lines "ABCDEF..."
  by "cat"-ing them.
- Copy around a few binary files to flush the file cache.
- Re-examine the test files created.  The ones bigger than a few 100Kb
  will typically have one or more of the error patterns mentioned above.

The odd thing is that the last couple of days it happened two times
that the problem did *not* show up.  I could read in all the floppies I had,
and perform the above tests without problems.  I find it hard to believe
that it is (just) a problem with the CMOS/controller/disk settings,
because when I restarted the system after the two "successful" tries,
the problem reared its ugly head again.

By the way, with **DOS5.0 I didn't have this kind of problems, but I guess
that doesn't say much.  A colleague of mine has the same system at home,
with similar problems.

Does anyone here have a clue about what could be the cause of all this?

Thanks,
Kees Verstoep (versto@cs.vu.nl)