Josh Dersch wrote:
On Dec 27,
2008, at 7:19 PM, Steven M Jones <classiccmp at crash.com>
wrote:
A while back I grabbed a number of bare Q22
backplanes off of eBay
in case I found I needed to replace the backplanes on these systems.
Haven't gotten around to even assessing feasibility, but the plan is
to try and just swap the backplanes whole. I've got a handful of
KDJ11-A dual-height CPUs to use if that works, though I'll probably
need some MXV11's or something to go with them.
Jerome Fine replies:
A MXV11 (or other board with a bootstrap) is needed only when a DEC
controller
(without a bootstrap) is used. Most (probably all) 3rd party
controllers or host
adapters contain bootstrap code. Note that neither the M8186 nor the M8192
(KDJ11-A) contain a bootstrap (or a serial DL port).
Both the M8189 and the M8190 quad boards contain a bootstrap, although the
versions available with the M8189 are often restricted to RL02 / RX02
drives.
The bigger
question, to my mind, is how to cheaply attach disks.
With the VT103 I believe some folks have placed small disks (3.5"?)
under the CRT, where the TU58 drives would have been on a
PDT-11/130. But you still need a drive interface to talk to 'em.
Perhaps one of the Micropolis half-height ESDI drives would fit, and
work with your controller.
I have a number of external TRS-80 external hard-disk enclosures,
which at one point contained MFM-style drives -- since the cabling is
the same as ESDI I was considering putting an ESDI drive in one and
cabling it to the Emulex controller, thus allowing an external drive
and cutting down on space/power issues in the VT103.
An external hard disk enclosure is not essential. I usually just use a PC
power supply and a bare hard drive with the cables from the controller
hanging out the back of the VT103, especially when using an ESDI hard
drive which requires more power than an MFM hard drive. I suggest
that you also place a fan beside any ESDI hard drive since they usually
run very hot.
Note that an RQDX3 (dual board from DEC WITHOUT a boot ROM)
is probably quite reasonable with an M8190 and Qbus memory as far as
power is concerned. An RQDX1/2 (quad board from DEC WITHOUT
a boot ROM) needs 6 amps for the 5 volts and will often overload the
VT103 power supply when the other boards are added to the total needed
to run a minimum system.
As for placing the hard drive under the CRT, while there is ample room for
a 3.5" hard drive, I have managed with an ST412 5.25" hard drive - although
I agree that it was a VERY tight squeeze. A third party MFM controller
(with a boot ROM), M8186 / M8192, memory and DLV11-J are sufficient to run
RT-11 and the VT103 power supply is sufficient to support the ST412 as
well.
In addition I
see two projects out there for Qbus disk interfaces:
wintersweet:
http://www.mscpscsi.com/
CHD's Q22-ATA:
http://www.chd.dyndns.org/qbus_ide/
No further information, like availability or compatibility, and no
timeline for when I'll drag out the stuff I have and start
contributing ... ;^)
Man, One (or two!) of those things would be sweet! I lucked out and
snagged a CQD-220 SCSI controller off eBay for $80 last year, but I
doubt I'll ever find another SCSI controller for that price...
Was that a CQD 220TM? A CQD 220T will handle only a tape drive. If you
have a CQD 220TM that works, $80 is certainly a very low cost. It usually
supports optical disk drives as well and may support CDROM drives. In
my case, I have an Adaptec AHA 2940AU SCSI host adapter on my PC
and can use a Sony SMO S-501 media to move 295 MB from the real
PDP-11 to the PC running E11 under Windows 98SE. I am hoping that
E11 will also be able to use the optical drive under Windows XP, but I
will not know for about 6 months.
Sincerely yours,
Jerome Fine