30 Nov
1999
30 Nov
'99
11:47 p.m.
> 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?
Yes.
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
The non-SCSI disk controller is a ST506/SCSI board unpopulated in
the *other* direction - it lacks the SCSI chip and connectors, but
has the ST506 parts. There's a plain metal flange on the rear where the
external SCSI connector would be.
There are also, of course, 3100's without any disk controller in them
at all.
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.
I never got around to trying that particular combination (though I did
have a RX50 hooked to a VS2000 - it worked fine under VMS, but evidently
the built-in firmware didn't like it.)
> 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.)
Even faster, build standalone backup on a hard drive :-).
If you want to see slow, remember the process of building standalone
backup on TU58's on a 11/750 or 11/730? We're talking most of a *day*!
No wonder we've tried to erase those times from our memories :-).
--
Tim Shoppa Email: shoppa(a)trailing-edge.com
Trailing Edge Technology WWW: http://www.trailing-edge.com/
7328 Bradley Blvd Voice: 301-767-5917
Bethesda, MD, USA 20817 Fax: 301-767-5927