DEC KM11 Question

Dave McGuire mcguire at
Sat Jun 20 12:01:21 CDT 2009

On Jun 20, 2009, at 12:15 PM, Rick Bensene wrote:
> I recently acquired two complete original DEC KM11 maintenance panel
> board sets (the board with the four toggle switches and bank of
> incandescent lamps) and the other "extender" board with the
> transistorized drivers for the lamps.
> From what I've been able to tell, these boards can be used for
> diagnosing things at the microcode level on (at least) the first
> generation microcoded Unibus PDP 11's (11/35, 11/45, 11/05) as well as
> diagnosis of the RK11 disk controllers (with an appropriate plastic
> overlay for the indicator lights).  The question I have is can this be
> used on an 11/34a to step through the microcode?
> The 11/34a runs fine so I don't need them for actual diagnostic work,
> but it'd be at least cool to try out the KM11s (I understand that two
> are needed) and watch the lights if they in fact will work on the
> 11/34a.  I've dug around in the usual places to try to find the answer
> myself, and have come up empty.  Also, if the KM11 can be used on the
> 11/34a, does anyone know of documentation that explains how to use  
> it in
> this context?

   The KM11 predates the 11/34 by a few years...I wonder if it can be  
used in that machine at all, I kinda doubt it.  The KY11-LB front  
panel, if properly equipped with the two additional (10-pin I think)  
"maintenance" cables, can be used to single-step microcode in the  
11/34 CPU.


Dave McGuire
Port Charlotte, FL

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