SCSI Woes

[Gurm]

Well folks, here is a request for aid in a long string of SCSI woes.

I have a controller... an Adaptec 2940UW. Latest BIOS, etc.

I have two internal devices on the standard SCSI ribbon - a Toshiba DVD drive and a Plextor 12x4x32 burner.

All is well. Things work fine.

HOWEVER, if I plug my external zip drive and/or scanner in on the external connector, the burner stops working. It will sporadically not enumerate in the BIOS, and even when it does it usually won't burn properly.

My solution until now has been to run the external devices off a little baby ISA SCSI card. However, this slows down the whole system, provides piss-poor performance for the external devices, and takes up a slot which I am beginning to need.

So... ideas as to why this happens? The line was properly terminated, but errors kept occuring and termination cut in and out (as determined by a diagnostic terminator at the end of the chain)... now mind you this ONLY happened when the Plextor drive was hooked up!

I could make the problem go away by unhooking the Plextor, but it's a nice drive. I swapped it out for another, but it demonstrated the same problem. I've heard from other people online that Plextors are very picky about what else is on the SCSI bus... but this is ridiculous. If it's properly terminated all my deviced should work, right?

Ok, any ideas? Let me know.

- Gurm

------------------
Listen up, you primitive screwheads! See this? This is my BOOMSTICK! Etc. etc.

[Rakido]

Gurm,

does this help?
http://ask.adaptec.com/cgi-bin/tic/s...=2940%20extern


Rakido

[Rakido]

or this here:
http://ask.adaptec.com/cgi-bin/tic/s...=2940%20extern


Rakido

[Duty]

Hey,

A few questions:

Is the Plextor the last in the chain?

What are the positions of all the objects (DVD 1, Plextor 3...)?

What is the transfer rate set to for the channels in the SCSI Bios? Transfer max rates were known to cause problems with some devices on earlier models of the 2940's the card was trying to set the channels to support wide devices when the devices could not handle it.

Is there proper termination to the internal and external devices?


Jeff

------------------
Remember when naps were a bad thing?

-------------------------------
You stop learning when you are die, and some people just don't know the're dead yet!
-------------------------------
ABIT BP6 - 2 x Celeron 500 - 256MB Ram - MX300 - 3Com 509c - 3com 905tx - Creative PC DVD 6x - G400 DH - DSL (True Love Here) - Win98 se - Win 2000 pro

[Taz]

Have you turned termination off on the controller, this you will need to do if you are using internal & external devices on the same SCSI channel.

[Gurm]

Thank you all for your responses. I have some good ideas now.

First off - I'm going to be swapping the 2940UW for an Ultra 160 card this week. Also I'll be running Ultra160 drives, so a simpler card is right out (of course I won't have any IDE drives any more either so it'll free up resources).

But I may discover with the nicer card and some nicer cables that the problem is moot.

I'll keep y'all informed.

- Gurm

------------------
Listen up, you primitive screwheads! See this? This is my BOOMSTICK! Etc. etc.

[The PIT]

It's true for the 2940uw. Sounds like some sort of termination problem to me though.

[Gurm]

This is a VERY early silicon 2940UW. It's entirely possible that it's messed up. The one I swapped it with to test is from the same batch, so it's possible that there's just a problem with early 2940UW's.

- Gurm

------------------
Listen up, you primitive screwheads! See this? This is my BOOMSTICK! Etc. etc.

[tufka dZeus]

where can you see the silicon version of the AHA2940?

just wondering, since I have a 2940UW too, and don't know how old it is... (got it second hand)

[superfly]

That's where 64 bit 66 mhz pci slots come in,they're about 4 times faster than standard pci(532mb/s),unfortunately they're only available on intel's 840 chipset,they're are a couple more companies that offer 64 bit/66mhz pci,but these are for high end workstations and servers not necessarily running windows either.

[SCompRacer]

Active termination on the scanner solved my Plextor problem. Passive termination caused all sorts of problems for the burner and the reader.

[Gurm]

Scompracer:

I put an active terminator (with diagnostics) on the scanner. It made the situation marginally better, in that the plextor often would in fact show up. But it would still seldom burn properly.

I suspect cabling, or card, or both. I'll let you all know next week though, once I've been able to thoroughly test the new rig.

- Gurm

------------------
Listen up, you primitive screwheads! See this? This is my BOOMSTICK! Etc. etc.

[Rick]

A quote I came across:

"SCSI is *NOT* magic. There are *fundamental technical reasons* why it is necessary to sacrifice a young goat to your SCSI chain now and then."