[Simh] Re: Simh Digest, Vol 7, Issue 2

[Ethan Dicks]

On Mon, Jun 14, 2004 at 04:40:39PM +0000, bsupnik at comcast.net wrote:
> 1. Older VAXen.
> 
> A 780 or 750 would require substantial changes to the simulator; indeed, it
> would be almost an entirely new simulator.  In particular,
> 
> - the CPU must support all the VAX instructions, not just the VAX subset.  That
> includes decimal, obsolete character string, H_floating, and EDITPC (argh!) 

Compatibility mode?

> - the boot and console protocol is based on an external microprocessor.  While
> that doesn't have to be explicitly emulated, all the proper firmware has to be
> found.

While the 11/780 and 11/730 had an external console and boot processor, I don't
recall seeing one in the 11/750.  Is it embedded on the console board?  Certainly,
the 11/780 and 11/730 were always soft-loaded, and the 11/750 normally came up
on its own read-only WCS memory that could be boot-time or run-time patched.

Not to say it's easy or not easy, just recollecting what I can of those machines.

Disclaimer: I've owned KA750 and KA730 machines, and I've only had user-level
access on 11/780-class machines.

I, too, would like to see an emulator for the older hardware, but I can see
how much harder that is than emulating a CVAX chip.

-ethan

-- 
Ethan Dicks, A-130-S      Current South Pole Weather at 15-Jun-2004 10:20 Z
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Ethan.Dicks at amanda.spole.gov     http://penguincentral.com/penguincentral.html