30 Nov
1999
30 Nov
'99
2:04 p.m.
From: Tim Shoppa shoppa(a)trailing-edge.com
>Didn't the very first 3100's have MFM
controllers? I could have sworn that
>I've heard that they did, but I've never seen such a beast.
Yes, the first 3100's had MFM controllers, and
half-height MFM drives
(RD31, RD32) in them. They also had a 34-pin floppy interface to a
non-SCSI RX23. Then came models that had *both* MFM and SCSI interfaces.
The latest ones had two SCSI interfaces, and used a SCSI-fied RX23 in
them.
I've never seen anything more primitive than the ST506/SCSI
controller. Was there really a non-SCSI board before that? Even the
earliest production ST506/SCSI boards in my experience lacked some or
all of the 20- and 34-pin connectors for the ST506 disks, but after I
added the connectors, I got an RD54 to work with one (for entertainment
only). The TEST 7x formatter looked to be on a multi-day jaunt when I
aborted it, but otherwise it was swell. Later, I found some (presumably
later production) ST506/SCSI boards which were missing a few 8-pin DIP
IC's and a few passive parts, no doubt saving a few dollars, but leaving
only the floppy interface intact.
The potential of DUA0 and DUA1 explains why the RX23 floppy is DUA2.
I always assumed that DUA3 would be the other half of an RX50, if it
were ever supported, but that was only an assumption. The firmware on
my 3100 systems seemed bewildered by an RX33, so I never bothered trying
an RX50.
True, the RX23 doesn't have a lot of use. You
can't even (officially)
build a standalone backup kit on it.
I modified the V6.2 STABACKIT to build a kit on (three) RX23
floppies, but some older firmware couldn't handle booting from them.
V1.5 is good, possibly V1.4 also, as I recall. Faster booting than from
a TK50. (Toggle switches would be _about_ as fast as a TK50.)
And speaking of TK50, for the record, the external SCSI version is a
TK50Z-FA (approved for the VAXstation/MicroVAX 2000) or a TK50Z-GA
(newer firmware, external SCSI ID switch). I tried a -FA on a VAX 4200
with a KZQSA SCSI board long ago, and I use one on my VAXsta 3138 now,
and have never had a problem. Has anyone actually had a problem using a
-FA in a modern environment? (That's "modern" compared to a 2000, of
course.)
As for the smallest VAX, I'd vote for the VAXstation 3100 (model 38,
WS42-xx, is faster than the original model 30, VS42-xx), as the
smallest, practical, bargain system. A minimal 2000 is smaller, but add
an external disk drive and the 2000 is bigger, and any 3100 with even
one decent SCSI disk beats it easily for storage and speed. (It's not
hard to beat two RD54 drives, unless all you have is RD53 drives.) Herr
Moeller's PK2K SCSI port driver for the 2000 should help total storage,
but the firmware still needs an RDxx from which to boot (or an RX33 for
Standalone BACKUP). The 3100 permits more memory and better graphics,
too. I'm not throwing away my 2000, but I wouldn't start with one
today, unless it fell on me (as my first one did).
------------------------------------------------------------------------
Steven M. Schweda (+1) 651-645-9249 (voice, home)
1630 Marshall Avenue #8 (+1) 612-754-2636 (voice, work)
Saint Paul MN 55104-6225 (+1) 612-754-6302 (facsimile, work)
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