Reanimating a PDP-11/23

Pete Turnbull pete at
Mon Nov 30 16:34:04 CST 2009

On 30/11/2009 20:50, Pontus Pihlgren wrote:

> I've been trying to get my 11/23 back on its feet. I've tried the 
> following setup:
> KDF11-AA (M8186, CPU) 
> MSV11-DD (M8044-DD, Memory) 
> DLVJ1-M  (M8043, SLU)
> BDV11    (M8012)

> In both cases I see nothing on my terminal (I tried both a vt100 and 
> vt320) were I think I should see the ODT @-prompt.

If you're using a DE-9 connector cable on a microPDP-11/23, or the cab 
kit belonging to one, the pinout isn't the same as the common modern PC 
version, as Ethan pointed out.  If you're using a 25-pin D-connector on 
some other cabinet kit, make sure you have Tx and Rx (pins 2 and 3) the 
right way round, and signal ground (pin 7, not the same as protective 
ground on pin 1) connected.

If you're using a 10-pin berg-style connector directly onto the DLV11-J, 
check it's made up correctly; it has differential signals and you need 
to link pins 7 and 9 to make it work properly (though I'd not expect 
that to stop it transmitting.  The other pins you need are Tx+ on pin 3, 
Rx+ on 8 pin, and ground on pin 2.

Whatever you're doing, make sure you have the baud rate set correctly. 
If the speed is wildly out, you may see nothing.  If you have Tx and Rx 
mixed up, you will see nothing.  And on a DLV11-J, make sure you're 
using the correct port -- only port 3 can be the console port (the one 
on the extreme left as you look at it from the back) -- and that it is 
actually set up as a console, and that the DLV11-J is set to the 
standard address.  You can set a DLV11-J *not* to reserve one port for 
the console, and you can also set it to different start addresses 
(though that shouldn't, in itself, affect the console port, if it's 
configured to provide one).

Unlikely to be wrong, but do you have the cards in the right places in 
the backplane?  If this is a serpentine backplane, they should be in 
slot 1 AB, then slot 1 CD, slot 2 CD.  If it's a straight backplane 
(standard for an 11/23) they should be one under the other, with no 
cards in the CD section (except, of course, the BDV11 which take up all 
4 sections of the slot).

> Also, the AUX on/off switch does not work, how is it connected to the 
> PSU?

If this is a standard BA11-N or BA11-S box, or anything similar, that 
switch isn't connected to the PSU, exactly.  It is usually jumpered to 
enable/disable the LTC signal, but it can be cabled to the rack's power 
controller using a 3-core cable with a 3-pin AMP Commercial Mate-N-Lolk 
connector on each end.

Pete						Peter Turnbull
						Network Manager
						University of York

More information about the cctech mailing list