[Simh] Vax 11/780 with multiple CPUs?

[Boucher, François]

From: "Hittner, David T (IS)" <david.hittner at ngc.com>
Subject: Re: [Simh] Vax 11/780 with multiple CPUs?


>It seems to me that if you want to see multiple VAX CPU support, it would be better to simulate a more popular and well >documented system, such as the VAX 6000/7000 series.

I agree with you, David.  In fact, i have under hand a working vax 6000-640 with 4 CPUs, console, 512MB ram,
double ethernet interface, CI BUS interface.  I would certainly not be unhappy with developping a multi-CPU VAX 6000
simulator, but I thought it would be a shorter path to go to a multiple CPU vax 11/780 or later machine, as the software
base for the simh devices is mostly already there.  I am not stuck with the 11/784, as a 11/782, 11/787 could be interesting
also to implement as they are dual cpu vaxes.
 
Your suggestion to go to the vax 6000 series does not mention the feasability to modify SIMH to be able to simulate
multi-cpu machines with some sort of multiple CPU-only processes on multi-CPU host machines (quad cores machines
for example).  The idea being to be able to use one host-core CPU per emulated CPU.

>As you point out, the 11/784 was such a rare beast that you would probably be hard-pressed to find decent documentation. >Nor would you likely be able to find real hardware to compare the simulated behavior against.  :-)
Probably as for the vaxserver3900, that simh implements.  Simh is for vintage computing machines emulation, before
they fall into complete history.  If there is no more doc or console files available to create a simh, well the machine is 
now already into history!

>Also, AFAIK, VMS dropped support for the 11/784 at one point, due to no longer having a working model on which to >verify behavior, just like they dropped the MicroVAX I, the 11/725, the 11/782, the MicroVAX 2000 etc...  :-(

We are all certainly aware that we are not working with supported machines... nor supported software anymore.
But the old VMS versions (ie VMS 5.5-2) of the time certainly supported those vaxes.

François



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