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From: hm@hcshh.hcs.de (Hellmuth Michaelis)
Newsgroups: comp.os.386bsd.misc
Subject: Kernel panics, SCSI cables and a 1742 in enhanced mode
Date: 9 Feb 1994 19:37:24 +0100
Organization: HCS Hanseatischer Computerservice GmbH
Lines: 46
Message-ID: <2jbah4$dua@hcshh.hcs.de>
NNTP-Posting-Host: hcshh.hcs.de
Keywords: SCSI (x)xxxBSD panic
A followup to an earlier article:
Two weeks ago, i added to the following configuration:
Adaptec 1742 running in enhanced mode
SCSI-2 disk (fast)
SCSI-1 disk (slow)
SCSI-1 tape
SCSI-1 cdrom
another SCSI-1 (slow) disk drive. From then on i got sporadic kernel
panics:
ahb0: timeout
ahb0: timeout
ahb0: timeout
AGAINahb0: timeout
panic ....
The access LED on the 1742 stayed on. The 1742 was totally frozen, the
power had to be cycled to make it work again.
After i replaced the cheap SCSI (50-pin Centronics-type) cable that came
with the drive with an expensive SCSI-2 compliant cable, everything ran
smooth as before. (at this point the previous post was made)
Then i reordered the devices on the SCSI bus, that is i changed nothing
but the location and the physical order of the devices.
As you might guess, it came again: ahb0: timeout .... panic ....
The fast SCSI drive had a sync xfer rate of 10Mb/s and an async rate of 5Mb/s.
The "new" slow one had a sync xfer rate of 4Mb/s and an async rate of 1.5Mb/s.
(These are the maximum values i got from the tech ref manuals)
In the 1742 user manual i found that if there are "hangs" and one has drives
of very diffent speeds on the bus, one has to adjust the maximum synchronous
transfer speeds in the EISA configuration - which i did, they are set at
10 Mb/s by default; i set the maximum speed for the "new" slow disk to 5Mb/s
and since a week everything runs fine (under heavy load).
SCSI is not just "plug and play" anymore ....
hellmuth
--
Hellmuth Michaelis HCS Hanseatischer Computerservice GmbH Hamburg, Europe
#define BSD4_4 0.5 (NetBSD 0.9 <sys/param.h>)