At 01:38 1/15/2000 , Mary Wolden wrote:
>My experience with SCSI termination has been that if the SCSI bus is
>terminated with the first drive then anything after the first terminated
>drive would not be recognized in either the SCSI bios or by the system.  I
>have always used the "Term Power from Drive" with no problems.
>
>Actually I am more concerned with the small power supply, 235w that he is
>using.  I had problems with a 250w power supply and 3 drives.  I
>bought a PC
>Power & Cooling 400w power supply for my 3 SCSI drives.  I also have 2 cd
>roms and the normal adapter cards on the motherboard.  On the 250w power
>supply I had many GPF's, partitions that diappeared and could not be
>written
>too, and the occassional disappearing drive on cold boots, the last drive
>would disappear and then my SCSI bus would not have the proper
>termination.
>I replaced the power supply and all of my problems have
>disappeared.  If the
>system works fine with one SCSI drive, then add another and it still
>works,
>add the third and see if you start having problems with the second or
>third
>drive.  I would then suspect the power supply is not sufficient for your
>needs.


Hi Mary

Quite right about the power supply. These three drives
use about 30 Watts apiece (at startup) and so would require
about 90 Watts. If Brad's 235 Watt power supply is a real
inexpensive one, it could very well be the problem. But it
wasn't long ago when large manufacturers were using 145 Watt
power supplies in their systems and Brad should have 145 watts
left (after the drives are taken account of) for the rest of
the system.  I was hoping that the problem was elsewhere...so
that Brad wouldn't have to replace the power supply right away.
That could mean delays.

I have three 400 Watt power supplies and one 300 Watt supply
in my four PCs. All are from PCP&C or CalPC (who supply PCP&C).
I'd bet that they are of such quality that I could go well
over spec as to power. (I have 7 drives in one of these
systems.) These power supplies cost more than most cases and
power supplies combined

I have seen cases where the middle of the SCSI bus is terminated
and devices further out were still recognized. It depends on the
geometry of the bus how well things work (if at all). A shorter
cable is a help in such cases. (Nobody would try this on purpose
of course.

I've made enough stupid errors myself that I know how easy it
is to get a SCSI ID wrong or to mess up the termination...
particularly when the drives are in the case and you need a
flashlight to see the jumpers. For example, I had a Seagate Hawk
set as terminated a few weeks ago. The shunt was so small that I
didn't see it when I moved the drive from one bay to another.
The result was seven drives with both the middle drive and the
last drive terminated. I could see all drives at boot but I when
I created partitions on one of the drives, they disappeared
upon rebooting. I also had problems using the SCSI CDROM drive.
It would work after booting for a while and then start giving
(Abort, Retry, Cancel) errors. I've also had problems using
older hard drives which need more power...two full height
drives (at 60 Watts apiece) that wouldn't work with a smaller
power supply.

I find it suggestive that at lower speeds, Brad's problems
are less severe in the sense that at least Windows would
boot and he could see all the drives in the Adaptec BIOS.

Regards,
Bill

            Do you want to signoff PCBUILD or just change to
                    Digest mode - visit our web site:
                    http://nospin.com/pc/pcbuild.html