Very Computer

thanks,
- dink ( http://ozbbs.ml.org/dink )

->When I copy lots of stuff off of cdrom(s), sometimes the system will hang
->or just trap(it happens randomly).  I have an IBM 4.5gig uw scsi drive on the
->68pin connector,
->toshiba 32x and ricoh 6200s(cdr) on the 50-pin connector, everything is
->(or seems) properly terminated.  anyone have suggestions or ideas?
->It only happens after/while using the CD drives.

Classic symptoms of termination and/or cable problems on SCSI. Doublecheck
everything that you think is correct - it's easy to get it wrong. Check
the 2940UW BIOS for the auto-termination option and turn it off - specify
how you want termination set on it, don't let it work it out for itself.

Trevor Hemsley, London, UK

:
:->When I copy lots of stuff off of cdrom(s), sometimes the system will hang
:->or just trap(it happens randomly).  I have an IBM 4.5gig uw scsi drive on the
:->68pin connector,
:->toshiba 32x and ricoh 6200s(cdr) on the 50-pin connector, everything is
:->(or seems) properly terminated.  anyone have suggestions or ideas?
:->It only happens after/while using the CD drives.
:
:Classic symptoms of termination and/or cable problems on SCSI. Doublecheck
:everything that you think is correct - it's easy to get it wrong. Check
:the 2940UW BIOS for the auto-termination option and turn it off - specify
:how you want termination set on it, don't let it work it out for itself.

Replaced the cables, checked the terminators, for the 20th time =)
yea, why would I need autotermination if I have terminators.. hmm

Ok, about the auto-termination...  It has weird options like:
Low/High
High/Low
.. and autotermination

You're probably saying, rtfm... but my adaptec manual burnt in a house
fire.. about 2 months ago =(  

Anyways, any help would be very much appreciated =)

- dink ( http://ozbbs.ml.org/dink )

->Replaced the cables, checked the terminators, for the 20th time =)
->yea, why would I need autotermination if I have terminators.. hmm
->
->Ok, about the auto-termination...  It has weird options like:
->Low/High
->High/Low
->... and autotermination
->
->You're probably saying, rtfm... but my adaptec manual burnt in a house
->fire.. about 2 months ago =(  

From the manual then.... (best viewed in System Monospaced)

Device connected to AHA-2940UW  Low     High
68pin internal connector only   on      on
68pin external connector only   on      on
68pin internal and 68 external  off     off
50pin internal only             on      on
50pin and 68pin internal        off     on
50pin internal and 68pin ext.   off     on

Caution: DO NOT connect SCSI devices to all three connectors of an
AHA-2940UW.

So, if you have the following setup

|-----------|-----------|-------------|
|           |           |             |
wide      2940UW       CD            CD-R
disk      adapter      drive

then you will need to make sure that the wide disk has termination
enabled, the 2940UW is set to low off/high on, the CD is unterminated and
the CD-R is terminated.

In addition since the disk is ultra and runs at ultra speeds and you have
4 or more devices connected to the SCSI bus (2940UW counts as one) then
you should restrict the *total* length of all cables to 1.5m or less -
that's the length of both 68pin cable plus the 50pin cable should not
exceed 1.5m in total.

Also to stay within the spec, if you are using _any_ ultra devices at
ultra speeds then all terminators *must* be active and not passive. If you
are using the termination on board one or other of your 50 pin devices it
is highly likely to be passive termination - you may need to look for a
separate 50pin active terminator. You may be able to get away without
using active termination but it's probably worth trying to switch
whichever of your 50pin devices is currently at the end of the cable over
for the other one in the hope that it will do a better job of terminating
the bus. CD drives, for example, are notoriously bad at termination!

Trevor Hemsley, London, UK

Quote:>Caution: DO NOT connect SCSI devices to all three connectors of an
>AHA-2940UW.

Quote:>In addition since the disk is ultra and runs at ultra speeds and you have 4
>or more devices connected to the SCSI bus (2940UW counts as one) then you
>should restrict the *total* length of all cables to 1.5m or less -
>that's the length of both 68pin cable plus the 50pin cable should not
>exceed 1.5m in total.

Which is why I'm using a SYM22801 DUAL CHANNEL UWSCSI card... :) beautiful
piece of work, both in the appearence AND the way it worked! :)

Quote:>Also to stay within the spec, if you are using _any_ ultra devices at ultra
>speeds then all terminators *must* be active and not passive. If you are
>using the termination on board one or other of your 50 pin devices it is
>highly likely to be passive termination - you may need to look for a
>separate 50pin active terminator. You may be able to get away without using
>active termination but it's probably worth trying to switch whichever of
>your 50pin devices is currently at the end of the cable over for the other
>one in the hope that it will do a better job of terminating the bus. CD
>drives, for example, are notoriously bad at termination!

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John Youells
LifeStream Computing

Quote:>I've narrowed the problem down to my 100mhz bus speed, I changed it to
>66mhz and everything works fine.  A few people (on irc) say the 2940uw card
>has problems with 100mhz bus... i'm not sure....

Quote:>fyi, i've tried 3 other DIMMS (pc100), 2 other motherboards and 2 diff.
>video cards, so the only thing that could cause the problem is the 2940..
>I'll call adaptec on monday and see what they have to say..  

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:>
:> When I copy lots of stuff off of cdrom(s), sometimes the system will hang
:> or just trap(it happens randomly).  I have an IBM 4.5gig uw scsi drive on the
:> 68pin connector,
:> toshiba 32x and ricoh 6200s(cdr) on the 50-pin connector, everything is
:> (or seems) properly terminated.  anyone have suggestions or ideas?
:> It only happens after/while using the CD drives.

I've narrowed the problem down to my 100mhz bus speed, I changed it
to 66mhz and everything works fine.  A few people (on irc) say the
2940uw card has problems with 100mhz bus... i'm not sure....

fyi, i've tried 3 other DIMMS (pc100), 2 other motherboards and 2 diff. video
cards, so the only thing that could cause the problem is the 2940.. I'll call
adaptec on monday and see what they have to say..  

- dink ( http://ozbbs.ml.org/dink )

Quote:> >I've narrowed the problem down to my 100mhz bus speed, I changed it to
> >66mhz and everything works fine.  A few people (on irc) say the 2940uw card
> >has problems with 100mhz bus... i'm not sure....

> I don't think so, because PCI bus stays at a constant 33.333MHz... I think
> you might want to see if the driver might have a problem when the computer
> is a little too fast (like W95... :) )

Ron

Quote:>You did change the PCI bus divisor strap, right.  At 66 you should be
>dividing by 2 and at 100 dividing by 3.

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:> >I've narrowed the problem down to my 100mhz bus speed, I changed it to
:> >66mhz and everything works fine.  A few people (on irc) say the 2940uw card
:> >has problems with 100mhz bus... i'm not sure....
:>
:> I don't think so, because PCI bus stays at a constant 33.333MHz... I think
:> you might want to see if the driver might have a problem when the computer
:> is a little too fast (like W95... :) )
:>
:You did change the PCI bus divisor strap, right.  At 66 you should be
:dividing by 2 and at 100 dividing by 3.

Theres no option in my BIOS to do that =(

Quote:>:> I don't think so, because PCI bus stays at a constant 33.333MHz... I think
>:> you might want to see if the driver might have a problem when the computer
>:> is a little too fast (like W95... :) )
>:>
>:You did change the PCI bus divisor strap, right.  At 66 you should be
>:dividing by 2 and at 100 dividing by 3.
>Theres no option in my BIOS to do that =(

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Quote:> >You did change the PCI bus divisor strap, right.  At 66 you should be
> >dividing by 2 and at 100 dividing by 3.

> You do not need to do that... If the chipset and motherboard designer have
> half a brain, they would design it so that when you use 100MHz, the 1/3
> divider would automatically be enabled... :)

Ron

Quote:> Theres no option in my BIOS to do that =(

Ron