[HECnet] SIMH TOPS-20 question

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.