compact pdp11 and front panel - test-drb@ccmp.vtda.org

2 Mar 2009

Qbus -11s are poor candidates as they are hard to stall.  That said you can display 
the dynamic address and data.  This does meand latching the multiplexed address and
data and providing led drivers for that.  Also note as Chuck has said very little 
of the CPU state is brought to the bus so you cannot see 11/34 or 11/70 style 
info.  To be able to write to memory or incrementially display a location is far 
harder as the CPU is continiously active and hard to stop and restart without 
some code.

A switch flipping blinkin lights front pannel for an 11 is not simething I've missed
and I"ve run 11/34s and 11/70s.  In both those cases they were never used or needed.

Allison

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Subject: Re: compact pdp11 and front panel
   From: Dave McGuire <mcguire at neurotica.com>
   Date: Mon, 02 Mar 2009 12:11:44 -0500
     To: "General Discussion: On-Topic Posts Only" <cctech at
classiccmp.org>
     Cc: cctalk at classiccmp.org

On Mar 2, 2009, at 4:33 AM, David Griffith wrote:
  Does anyone know anything about shoehorning a
front panel with lots  
 of lights and switches onto a compact pdp11 (say, a /73 or /83)? 
   I don't know anything about it specifically, but just from  
thinking about it...I think the best you'd probably be able to do is  
address and data LEDs, plus RUN, and maybe a few others...not much  
more (i.e., no address spaces, processor states, etc) because the  
signals aren't brought out to the pins on the J11 chip.

   But if that'd be enough, you could probably do it by using some  
buffers to drive the LEDs, and doing DMA cycles onto the bus for the  
switches.  I'd probably take a whack at it if I had some time.

            -Dave

-- 
Dave McGuire
Port Charlotte, FL 