[TriLUG] LVD and SE SCSI question

[Jeremy Portzer]

On 2 Aug 2002, Tanner Lovelace wrote:

> Hi folks,
> 
> This may be a stupid question, but does anyone know what might happen
> if, say, an LVD SCSI drive is put on the same cable with a few SE SCSI
> drives? :-[ I've been trying to figure out why the SCSI card in the
> machine the CPD donated has been flaking out and on a whim this evening
> I looked up the complete drive specs and notice that one of the drives
> is LVD scsi.  Now, the card supports LVD scsi, but I'm afraid I may have
> messed things up by putting them both together.  I'm hoping, however,
> that by either just separating them, or by finding a jumper for the
> jumper on the LVD drive labeled "Force Single Ended" will fix things.  
> However, since I'm not a SCSI expert, I'd like to hear a few more
> opinions.

Tanner,
There is a guide for the ST118273LW on Seagate's web site:
	http://www.seagate.com/support/disc/iguides/scsi/67512c.pdf

It's apparently not a good idea to mix LVD drives with regular
(single-ended) ones . The manual says (page 31):  "Do not mix "W","WD,"
and "LW" model drives on the daisy chain."  W are the normal drives (W for
wide) and LW are the LVD drives.

What kind of termination were you using?  Are you sure you had the right 
kind of terminator, and cable lengths were within spec?  Did you have 
the terminator power setting jumpered appropriateley?

There are a myriad of different configurations; see that pdf for details.

Regarding termination and the other Seagate drives, the manual says this:
"W  model drives are terminated with permanently mounted IC active 
terminators. If you install one of these drives and it is not on the end 
of the SCSI bus, disable the terminators by removing the jumper  TE  from 
pins 15 and 16 of connector J2. If you install the drive on the end of the 
SCSI bus, enable termination by installing a jumper on pins 15 and 16 of 
connector J2 (see Figure 13)."  (page 49)

Hope this helps,
Jeremy

(SCSI can be confusing!)