compact pdp11 and front panel

[Allison]

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



>
>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