[HECnet] SIMH TOPS-20 question

[Thomas DeBellis]

The PANDA distribution will work only if he wants a KL class installation.

I don't recall the state of the KL implementation for simh, but it 
didn't have one for some time.  It is reputed to have one now, but I 
couldn't speak to the suitability for Tops-20 7.1.  It could do a KS 
just fine.  Obviously, if simh can run a stock PANDA, then that would be 
of 'interest'

BUT!!

Another issue is that simh and klh10 implement different paradigms to 
indicate that the booted operating system is in the idle loop.  simh can 
be set to deduce this if the PC is executing for some period of time 
between a range of locations.  This will work for any operating system, 
assuming you know what those addresses are.

MRC pretty much despised it.  klh10 implements a special device called 
the 'Idler' for the PDP-10 OS to signal the host.   If you do a 
particular kind of I/O to the Idler (which can be set to be at different 
address), you are _directly_ telling klh10 that you are in your Idle 
loop.  This /extremely/ efficient as the signal is immediate.  A later 
version of PANDA that did not go into general distribution extends the 
Idler to implement some additional functionality, such as reading the 
switch register and displaying console lights, which Tops-20 had not 
been able to do since TENEX.

Another fine feature of the Idler is the 'heartbeat'.  Real KL's have a 
light that blinks on and off as kind of a talisman.  So, no blinky tells 
you something is very wrong (of course, another way to instrument that 
is by telephonic temperature, meaning they're glowing white hot with 
everybody calling...)

This can all be displayed by the PANDA front panel, which Bob could 
speak to better than I can.  The design is extensible enough to have a 
virtual front panel, perhaps python based, which I started on, but had 
to put aside due to being in a DECnet rabbit hole.

> ------------------------------------------------------------------------
> On 12/24/21 3:17 PM, Peter Lothberg wrote:
>
> Take MRC's "Panda distribution" if you just want
> it up and runnning.  I'ts somwhere on trailing edge..
>
> -P
> ------------------------------------------------------------------------
>> From: "R. Voorhorst"<R.Voorhorst at swabhawat.com>
>> To: "hecnet"<hecnet at Update.UU.SE>
>> Sent: Friday, December 24, 2021 2:46:15 PM
>> Subject: RE: [HECnet] SIMH TOPS-20 question
>>
>> Which Tops20 tape gives problems?  Try tpc, that sometimes is the problem.
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