Re: SCSI Termination Power

[Randy Shackelford <shack@onyx.southwind.net>]

John E. Townsend <utownje@lexis-nexis.com> wrote:
: OK, I finally got ahold of the HS SCSI utils disk for the IIe.
: Unfortunately it turned out to be pretty worthless, but I was able to do
: what I needed by cannibalizing the RamFAST out of my IIgs temporarily.
: Now I have another problem. :-)  The drive I want to use on the IIe (a
: 1988 vintage 40MB 3.5" Quantum mechanism that I took out of a Mac SE/30)
: doesn't seem to be providing SCSI termination power.  I figured this out
: after the drive would work on the RamFAST but not the HS SCSI card
: unless I added another device to the chain.  Since I really only want
: the Quantum drive on this machine, how can I get it to provide its own
: termination power?  There is a jumper block inside it with three pairs
: of contacts labeled SS, EP, and WS, and currently only the EP contacts
: are closed.  If necessary, I'm not afraid of using a soldering iron
: either. :-)

Going from memory, WS is the wait-spin connector and EP is a parity check
on Quantum drives. Wait-spin makes the drive wait to spin up until a signal
comes across the bus telling it to spin. I forget what SS does. Neither it
nor the WS are used typically.

The way to get terminator power is to use an enclosure which provides it. In
my old APS ZFP enclosure, there's a wire running directly from the power
supply to one pin on one of the Centronics connectors. It's pin 38 if I'm 
remembering right. Its job is to ensure terminator power, and that enclosure
works great on all my boxes, even the IIgs, Mac Plus, and Powerbook. None
of these provide terminator power themselves. However most of the boxes I use 
regularly, IIgs included, have devices with APS SR2000 or Pro enclosures
on the chain. These have APS' digital active termination, which takes care
of problems like terminator power.
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