[ On Wednesday, October 29, 2003 at 13:53:13 (EST), Robertdkeys@aol.com wrote: ]
> Subject: SS20 class machine problems in 1.6.1 or current?
>
> Are there issues in SS20 class machines in NetBSD 1.6.1
> or 1.6-current that would cause instability in the scsi bus,
> particularly as to reading of cdroms?
>[[ ... ]]
> It seems to suggest some possible scsi bus
> timing issues, but I can't quite put my finger on it exactly.

Yes, that's probably it.

SCSI instabilities, especially with traditionally "slow" devices such as
CD-ROMs and tapes, are typically electrical or signalling problems with
the bus, usually caused by poor termination or broken cabling and/or
connectors.

If your bus termination isn't perfect, then you will have problems (on
any system, including any Sun).

Do you have external devices?  If not do you have a proper "active" for
"FPT" terminator attached to the external connector?  The bus stub on
the motherboard to the external connector is just long enough on
sparcstations with internal SCA backplanes and internal CDs that it can
cause signal reflections if it's not properly terminated.

(You'll see that the inside half of the bus is terminated on the SCA
backplane for the disks, and the CD is just a stub off the inside bus
between that backplane and the motherboard, so it should not be
terminated onboard.  SCA disks are never terminated onboard.)

You may also have problems if you've got devices that attach as "sync"
with different speeds on the same bus.

BTW, I find the esp driver in netbsd-1-6 to be a _lot_ better behaved
than it was back in 1.5.

-- 
						Greg A. Woods

+1 416 218-0098                  VE3TCP            RoboHack <woods@robohack.ca>
Planix, Inc. <woods@planix.com>          Secrets of the Weird <woods@weird.com>