On Thursday 04 December 2003 08:50, Josiah Ritchie wrote:
>Gene Heskett scripted ::
>>As long as *both* ends 0f the cable are terminated, you should be.
>>The drive, if its terms are off, can be anywhere along the cable as
>>long as the far end is properly terminated.
>>
>>OTOH, if the drive is the far end termination, then the cable must
>> not go more than 1 or 2 inches max past the drives connection
>> point, else the echo's will come back from the untermed end of the
>> cable, leading to all sorts of weird data errors.
>
>Looks like I have that worked out. The termination on one end is the
> card and on the other end is built into the cable, some black
> plastic and what looks to be a pc board. I'm assuming that is a
> terminator and it's right on the end of the cable so no need to
> worry about short distance. (It's an HP cable if that makes a
> difference.)
I don't know for sure, not having any genuine HP cables. However,
this does bring up one other point that should be checked. The fact
that its on the cable means that its assuming the term power is
supplied from the host card via pin 25 IIRC. Double check that pin
number against what you have that could correct me, and then verify
that the card does indeed have its term power jumpers set to furnish
term power for the rest of the devices on the cable. This is
normally isolated by a diode so that if some other device on the
cable is also supplying term power, it cannot backfeed into the host
system when the host system is powered down.
Manufactureing cost cutters often force the production floor to use a
cheap si diode in that location, resulting in the term power only
being 4.4 volts or so. Usually that works, but it does make the
logic high level a bit low, and the cable then susceptable to
termination echos that might impinge on this lowered noise margin.
If thats the case, you might have someone familiar with hot solder
change that diode out for a suitable schotkey(oops, spelling) type,
or even a germainium power type, thereby raising the logic one
resting voltage enough to double the noise margin. The target
resting voltage should be 2.9 to 3.0 volts for the normal scsi bus.
Only 2.6 volts, due to the above cheap diode effect, can be a major
PITA. Your 500 to 600 millivolt noise margin has been reduced to 200
millivolts. Thats definitely "bad dog".
>Now I've done'tar tbf 64/dev/nst0' which listed lots and lots of
> files but ended in the error:
>
>tar: Skipping to next
>tar: Error exit delayed from previous errors
>
>I didn't notice any error prior to that, but they went by pretty
> fast. :-) It didn't list anything after that and returned me to the
> prompt. I've seen this with tar outside the context of a tape drive
> and I seem to remember that there was corruption in the tarball.
> I'm assuming that holds true here.
>
>I'm going to keep on going with the rest of Jay's directions as it
> looks like they test something else but would like to know what
> this means and if I still need to mess around with some setting or
> something to get this right.
>
>Thanks,
>Josiah
--
Cheers, Gene
AMD K6-III@500mhz 320M
Athlon1600XP@1400mhz 512M
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Yahoo.com attornies please note, additions to this message
by Gene Heskett are:
Copyright 2003 by Maurice Eugene Heskett, all rights reserved.
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