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Scientific Micro Systems 11X Computer

PDP-11/23 Compatible 1986

Last updated: 11 June 2018

Scientific Micro Systems 11X PDP11/23 Computer Roger Arrick
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Rescued this unmutilated OEM version of a DEC PDP-11/23 with CPU, memory, HD, 8" floppy and 8 serial ports made by Scientific Micro Systems around 1986.

My goal is to restore it, document it, and do some PDP-11 software development.

My email is ROGER at ROGERARRICK dot COM

What I Need - Please help if you can

I need bootable floppies and documentation. Utilities to work with the hard disk would be great. If you have these, please let me know. The brochure says this system can boot RT-11, RSX-11M, RSX-11M-Plus and TSX-Plus, and that it's compatible with RX02 disks so maybe it will boot a stock RT11 disk, I don't know.


Brochure from 1984
Another brochure

◼ 19" chassis 10.5" high with hinged top. Heavier than a dog house.
Model # DSX01174, Assembly # 1002003-0011 D
Label, back, front

Dual power supplies
OS251 by Optimal Systems Corporation. Picture
No documentation found.
One powers the DEC backplane and one powers the drives.
Both supplies are bad and have been replaced with modern switchers.
+5, -12, +12, +24

16-slot QBus backplane made by SMS
1 M8186 KDF11-A CPU board with 1 chip LSI 11/23 top, bottom
2 SMS disk controller cabled to another giant disk board then to HD and floppy. SMS zC2M top, bottom
3 Sigma quad serial (1st port displays boot prompt) top, bottom
4 Sigma quad serial
5 Kaiser & Damm, MOT 11 D1 with ribbon cable to, RAM and ROM, 6809, ROMs. CALMOT '83 top, bottom
6 Kaiser & Damm, MM07 (memory management?) 11.Aug.83 top, bottom
7-14 Unused
15-16 Camintonn CMV1000 memory board (probably 1mb) top, bottom

Disk Controller Board
The large disk controller board is mounted on the hinged top panel.
Cables go to the SMS board in the backplane then to both the HD and FD.

Hard Drive
label, top, bottom, Error Map.
8" Quantum Q2020
512 cyl, 4 heads, 32 sec/trk, precomp:256, landing 513, bytes/sec 256
Does not boot.

Floppy Drive
8" Double Sided
Shugart SA851


◼ Both power supplies were bad. Some components were changed to see if a fix was easy but no luck so replaced them with modern switchers.

◼ Two of the vibration isolators on the hard disk were broken. Replaced with same thing from McMaster Carr.


Upon reset, a boot prompt appears on one of the RS232 ports:
DRV(W0, F0, T)? which is asking Winchester, Floppy, Tape.
If I type F0 then the floppy drive selects and steps as if it's trying to boot.
I have no floppy disks.
After a few seconds without any input, it displays AUTO-BOOT
I assume this is the same as typing W0 for hard disk booting.
Nothing boots.
Then 173464 or 173310 or 173000 is displayed (probably failure addresses),
then ODT (Octal Debugging Technique) is entered.
ODT operates as expected.

PDP-11/23 Links

SMS stuff at bitsavers
PDP-11/23 at bitsavers
PDP-11/23 stuff at ComputingHistory
DEC forum at VCFED
alt.sys.pdp11 group
PiDP-11 group


My email is ROGER at ROGERARRICK dot COM

Everything is Always Under Construction

Copyright © Roger Arrick