Mounting a SCSI Device in a BA-123

From: Jerome Fine <jhfine_at_idirect.com>
Date: Sun Jul 29 20:10:37 2001

>Terry Murphy wrote:

> Has anybody ever mounted a SCSI device in a BA-123?

Jerome Fine replies:

Yes. And in a BA23 as well. In fact, the BA23 with the bad DRV11
has a CQD 220/TM with a 3.5" SCSI drive and a Zip 100 MByte
Iomega drive to handle removable media. Both drives are mounted
on the standard 5 1/4" black plastic sleds that used to hold an RD53
and an RX50. The 3.5" drive is held in place using two angle brackets
(90 degrees) that attach to the sled and the drive. The Iomega Zip
drive came with its own 5 1/4" adapter kit (it was a so-called SCSI
Insider). The cable used was a standard (about) 20" PC SCSI with
three 50 pin headers. There is JUST enough length between the
CQD220/TM and the hard drive (with about 0.1 mm to spare) to
be able to connect the two. And the extra length between the hard
drive and the Zip drive also JUST fits (with about 0.5 mm to spare).
The 50 pin cable comes through under the plate that allows for a TK50
cable.

> 1. I tried to install a standard half-height 3.5" SCSI drive into a
> BA-123 system (MicroVAX II). Basically, I bought a little 3.5"->5.25"
> adapter, and then screwed the adaptor into the sliding base where an old
> RD-54 lived. I found the solution unsatisfactory; the adaptor's screw
> holes did not match up with the sliding base, and it generally feels
> fragile. Is there a better way? I am envisioning some sort of "cage" which
> has the form factor of a full-height 5.25" drive, with mount points for a
> 3.5" drive (or two). Does such a beast exist?

While I agree that the DEC standard black plastic sleds are not easily
adapted, I was able to find a number of the angle brackets when I needed
them. If needed, they are just thin metal brackets bent at 90 degrees with one
hole as an anchor to hold the drive on each side and the sled. More is
unnecessary since the 3.5" drives are not heavy like the 5 1/4" drives.

> 2. Has anybody ever installed a half-height internal CD-ROM (or tape
> drive) in a BA-123 system? This would be really sweet (sure beats an
> external one!), but would it mount nicely, and would it be possible to
> cover up the half which isn't being used with a nice faceplate?

You can buy such plates for for cosmetic reasons, but I really don't find
it necessary for actual use. As for myself, I know that Zane has found a
SCSI CD-ROM which works on the actual PDP-11, but I have not
made the effort to find one. Does anyone have one for sale? I solved
my problem with a couple of Sony SMO S501 magneto optical disk
drives that are erasable and hole 300 MBytes per each side of the
cartridge. With one drive on the PDP-11 and one drive on the PC,
I can transfer up to 300 MBytes at a time between the two systems.

> 3. Is there a decent internal SCSI cable which can be used in a BA-123? I
> only have a couple of boards in the system, so my SCSI controller is all
> the way in the front of the backplane (back of the system), far from the
> disks, and just barely reaches the disks. Is it possible to get one with
> some slack, and still have several disk connectors?

The cable for the BA23 does not seem any shorter. So shifting to that
box probably will not help. If you can find a bunch of M9047 bus
grant cards, that would allow you to move the host adapter all the
way to the back. PLUS, I suspect that if you are not using the
ABCD aspects of the first 4 slots in the BA123 (unlikely unless you have
a uVAX II and must do so because the memory requires the ABCD,
then with a PDP-11, it is not necessary to use the ABCD slots for the
CPU unless you are using PMI memory.

Also, I don't think it is hard to make a longer SCSI cable. I have several that
have the 50 pin header at one end and a 50 pin centronics at the other that
are over 4 feet long. I just add as many 50 pin headers as needed to
accommodate any internal drives. But I only have one extra, so if I sold
it, I would charge what it would cost me in parts to replace it. Or if
you sent me double the 50 pin headers needed and one 50 pin centronics,
I could make one up for you. Better yet, make one for yourself with the
parts and an ordinary vice (large - at least 2.5" heads to tighten on the
parts) and a magnifying glass to look closely at the alignment before you
tighten the vice.

Sincerely yours,

Jerome Fine
Received on Sun Jul 29 2001 - 20:10:37 BST