760 MB SCSI for 4D/70-GT

[Knobi der Rechnerschrat]

Hallo networkers,

  Back August 89 I asked this list for help in installing a third-party
760 MB disk on our 4D/70-GT. I wanted to have a third party product for
reasons that are too obvious to raise the discussion again. We finally
got our disk installed for a reasonable price and I will describe my
experience to the net.

  Our machine is a 4D/70-GT with original 8MB memory and an 380 MB
ESDI disk on the 2-unit interphase controller. Back last year we decided
that we had an severe memory and disk problem. We cured the memory problem
first by buying 8 MB from a third party supplier (German company, not
interesting for the net). This worked fine, despite all "official" warnings
from SGI. Encouraged by our succes we dared to look for the disk. Our
choices have been to install a second ESDI disk or a SCSI disk. And we
wanted as much space as possible. We had to rule out the ESDI solution
(prefere for speed reasons), because our wouldn't support a 760 MB disk
"neither at speed nor reliable" (cited from Mark Bradley, SGI MV).

 So we looked into the SCSI solution. We had three devices in mind: the
CDC WREN VI (Model 94191), the Fujitsu M2263 and the Hitachi DK515-C-78. All
disks have about 770 MB unformatted and 16 ms average access time. The
Hitachi was pointed to us by Mark Bradley from SGI MV. His words were (as
I can remember): "We haven't tested the M2263 jet and for performance
reasons I personally would use the Hitachi drive". For price and delivery
reasons we finally decided to use the WREN-VI. Now was the question
how to install the disk. Mounting it in one of the IRIS cabinets? SGI MV
told us: "You can do that, but you have to provide enough air flow for
cooling and we (internally) have problems at higher temperatures". So we
opted for an external cage with power-supply. But how to cable that? Our
local SGI office  in Munich told us the solution: "Buy an ""HU-XSCI
Extendeable SCSI Module"" and your problem is solved". We did and it was.

 The module comes in two forms: a) a normal IRIS peripheral cabinet that
you put on top of your IRIS, or b) a replacement for the Bus-Board that
is usually installed in the peripheral cages, together with some cabling
and an external connector plate (+terminator). You have to replace
the bus-board and install cabling and the connector in the topmost module
of your tower (usually the tape I think). With both solutions you get the
same external SCSI connector as with the PI machines. You cannot install
SGI SCSI modules above the cage with the external connector, because the
SCSI bus is no longer connected (this is to prevent building a tree structure
I assume). If you exactly know what you are doing and if warranties and
maintenance are unimportant for you, I think one can just buy the cable.

  I have to thank SGI (Munich and MV) for the assistance they gave to
me. First they didn't like the idea of 3rd party stuff, but when I
explained our financial situation they were very helpful. My special
thanks go to Mark Bradley who is a very competent, helpful and kind
guy. I even could manange to stop his "You have been warned" comments
in his mail messages. I have been warned, but everything works fine and
we haven't broken our machine during the process of hardware installation.

  I hope this (somewhat longish) mail helps those people who are in the
same situation as I to get more disk space for a low price (and at their
risk) and to show that you can get more support from SGI when you are
polite (listening BLB and RD ?).

Regards
Martin Knoblauch

TH-Darmstadt
Physical Chemistry 1
Petersenstrasse 20
D-6100 Darmstadt, FRG

BITNET: <XBR2D96D at DDATHD21>

PS: Is there a way to switch on synchronous SCSI on the 4D-70? What are
    the risks?