Greetings all,
This is technically not a Linux specific question, more along the
lines of Ultra SCSI. But I'm hoping someone will have a quick
answer for me anyway.
I've got a Symbios 8751SP SCSI controller (53C825 based) - it's
Ultra-Wide. I've got the following setup internally:
+ Controller (ID 7)
+--- unused connection
+--- unused connection
+--- HP 1.1 GB HD (Fast - Narrow - ID 1)
+--- Sony CDU-76S 4x CD-ROM (Slow - Narrow - ID 6)
+--- unused connection
+--- Quantum Viking 4.5 GB HD (Ultra - Wide - ID 0)
Termination Enabled - Term Power enabled
For the Narrow devices, I have 68-50 pin adaptors.
Now, this all boots and runs just fine. I have the Quantum running
at 40 MB/s - the HP is at 10 MB/s and the Sony is at 5 MB/s - all as
expected. The HP does NOT have Term Enabled, and I've removed the
resistor blocks from the Sony (I assume that's correct, as I don't
have and can't find online any docs for the Sony).
Now, however, I'm trying to connect a Jaz 2GB drive (Ultra - Narrow -
ID3) to the external connector, and it's giving me lots of grief.
When I first tried this, I couldn't even get LILO to come up. Then
I removed the narrow devices from the internal chain, and I could
boot, but loading the kernel had a number of timeouts and other
problems. Despite that I was able to boot fully - and shutdown
right away again...
Finally, I jacked the Quantum down to 20 MB/s, (using the Symbios
BIOS setup), things got better, and I could connect the other internal
devices. But it's still having occasional timeout problems - say
one ever 5 to 10 minutes, depending on how heavily I use thing.
And they are all still on ID 0 (the end of the chain). This causes
the controller to reset the bus, which basically lock severything
up for 5-10 seconds. Needless to say, I'm not very comfortable with
this.
Now, the external cable is fairly high quality - cablestogo.com,
part # 08252 - SCSI MD68M - MD50M. It fits nice and tight. The
internal cable also seems of reasonable quality; it's a 7 device
cable I got from oscarno1.com. The 68-50 pin adaptors also seem
reasonable quality - oscarno1.com again. I have the Jaz setup
with Term enabled (rather than their Auto setting).
The internal cable is probably about 1 meter. The external cable
is about 3 feet. Could the length of the chain be causing me
problems? I've seen references that indicate that the total SCSI
length should be less than 1.5M for Ultra - I guess I'm exceeding
that slightly. Would moving all the internal devices closer to
the controller work. Are there any issues with the dangling cable
out there? Should I get a smaller (4-device) cable?
I've tried all kinds of things to try and get this to work,
but I haven't had any luck. I really want to get things working
reliably at their correct speeds. Any suggestions would be
greatly appreciated. I'm already toying with replacing the
CD-ROM, since it's the only slow device, but I don't think that
will help much.
Thanks,
Pete
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