[KLUG Hardware] Re: SCSI Question and Advice Request

[Thera]

Mike Williams wrote:

<snip>
> >
> Nice again.  Probably hasn't been cleaned in forever.

Some of the dust bunnies had teeth.

> 
> >The re-build is where the question comes in. Her SCSI cable has active
> >termination, but I noticed they had jumpered the 'SCSI Term ON' on her
> >solitary HDD. Doesn't this over-ride the active terminator on the cable
> >with a less desireable on-card termination ? ...or does it just say 'I'm
> >the last device on the chain so look for termination after me' ?
> >
> >
> Meaning the cable has a terminator block on the end of it?  Terminating

Yes.

> the drive then having another terminator is breaking the rules, but it
> probably works because the drive terminates the signal and the
> controller never "sees" the terminator.  Technically, you should have
> only one or the other, though.  

I'll remove the HDD jumper then. I was also confused because TFM says
that one or more of the devices must enable power to the active
terminator, and I wondered if maybe that's why they jumpered the HDD
'SCSI Term ON'. I've googled a spec sheet that shows those header pins 
as 'Enable SCSI Terminator', but I guess if it meant enable terminator 
_power_ it would have said so. (there are no such-labeled pins on any of 
the HDD headers). 

The mobo has on-board raid, so I'd gotten 3 of what I thought would be 
identical add'l HDDs with RAID 1+0 in mind. Turns out though the brand 
(IBM) and capacities are the same; the RPM, seek time, data rate,
transfer rate, etc... are not. They DO however, have 'Termination Power 
Enable' pins. So I'll use one of them. Just to be sure, I'll get them 
working strung out on the floor before I intstall them and their cages.

> Controller card termination is
> determined by how many of the card's connectors are used.  If you use
> only one connector (internal, external doesn't matter), you want the
> card's termination ON.  If you use 2 connectors you want termination
> OFF.  Most cards that have more than 2 (external, narrow internal, wide
> internal usually) require that you not use all 3 at once.

The SCSI controller is on-board the mobo, and is exactly as you describe 
(1 ext., 1 int., 1 narrow int.) I'll be using neither external, nor
narrow devices, so I'll enable termination on the controller end in the 
BIOS.

Thanks for your help :)

Thera