Adaptec termination problem...

[Grover Davidson]

I could be WAY out on this, but if memory serves me right,
the device that is FARTHEST away from the controller should
be terminated, regardless of its address. Termination, preferably
ACTIVE termination, belongs at the far end away from the controller.
Otherwise, the electrical charictaristics that termination is designed
to achieve don't occur.

I have a 2940W with:
	0:IBM Starfire 4.5GB Fast/Wide 
	1:Conner 540MB Fast
	2:Syquest 270MB
	4:IBM 8x CdRom (from an RS-6000)
	6:Exabyte 8200 8mm tape drive

My Wide cable has 1 activer terminator on it at the far end, and
my IBM drive is also plugged in at the far end.

My narrow bus has things plugged in in the order listed with the higher
addresses being farther from the contoller. My termination on the narrow
bus is supplied by the Exabyte with passive termination.

I have never had a problem with that layout. I have know a lot of
people who have had problems with their scsi system, and about 90%
of those were due to impropper termination.

You milage may Vary.

Grover
According to Stuart Park:
> 
> 
> On Sat, 23 May 1998, OLK wrote:
> > In theory (ANSI X3.170A-1991) you're right, but
> > as an owner of a computerstore after having built up many hundreds
> > of x86-PC's the facts have proven the opposite ;-(
> > Try 2xIBM+1xConner+CDROM with AHA-2940 and you'll see only one
> > combination
> > working :
> > IBM=ID0,IBM=ID1,CDROM=ID2,Conner=ID3 or higher and Terminated.
> > Chances are 99.9%, that all other combinations especially with one
> > terminated IBM-HD and other(IBM) not, will fail.
> > Rule of Thumb: Adaptec+IBM's+Whatever --> Desaster
> 
> I have a similar situation, but have the Connor drive at ID0 with
> no problems at all.  Maybe it's only specific models that are
> troublesome?
>   
> Configuration:  Adaptec 2940,
> ID0: Conner CFP1080S
> ID1: IBM DCAS 32160
> ID3: Sony CDU76S (cdrom)
> 
> (I can't remember at the moment which has the termination)
> 
> 
> Stuart Park
> E-Mail: stuart @ banana.psd.com.au            Melbourne, Australia
> 
> 
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-- 
Grover C. Davidson II 		(devildog at mo.net)
828 Fall Crown Ln               #include <std_disclaimer.h>
Fenton, Mo 63131     	 	Voice: 314-343-5642


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