[Simh] 750, 730

Bob Supnik bob at supnik.org
Mon Dec 29 15:16:55 EST 2008


What he said. ;)

Although the implementation of the full VAX instruction set means that 
emulation of new models is not as difficult as before, it's still rather 
complicated.  The 750 has its own version of the Massbus and Unibus 
adapters used in the 780, and they're not totally compatible. The 730 
has its own UBA and the integrated disk adapter. Each also has its own 
unique 'system bus' modules and memories.

I did the 780 to get coverage of software written before MicroVAX. 
Unless you have a software package that's unique to a different model, I 
don't see a compelling reason to do another VAX model.

/Bob
> Message: 1
> Date: Mon, 29 Dec 2008 08:28:42 -0600
> From: "Hittner, David T." <david.hittner at ngc.com>
> Subject: Re: [Simh] simh vax750 or vax730?
> To: "Brad Parker" <brad at heeltoe.com>
> Cc: simh at trailing-edge.com
> Message-ID:
> 	<30CEAB0BF6C5EC44AD20B91FD082037B02319C9A at XMBIL103.northgrum.com>
> Content-Type: text/plain;	charset="us-ascii"
>
> I suspect no has looked at creating (or will ever look at, unless it's
> you :-) a VAX-11 725/730/750 simulator.
>
> The main VAX of the SIMH project is the QBUS-based MicroVAX 3x00.
>
> The VAX-11/780 was added much later, for historical interest, since it
> was the original VAX. The creation process took a long time, and Bob had
> to re-engineer and re-discover many of the original components, as well
> as "hack"ing up a limited simulation of the LSI + floppy console
> subsystem to enable the system to boot.
>
> The VAX-11/725/730/750 had many different hardware components, which
> would require fairly extensive work to simulate. They all had different
> consoles; different cpu implementations; different memory controllers;
> the 730 had the CPU-assisted R80 (not RA80) disk and T80 (not TA80)
> tape; and the 725 had the dual-drive/single-spindle RC25 disk subsystem.
> The only thing that would make those simulator(s) easier to write is the
> ability to reuse the existing UNIBUS peripherals.
>
> Having worked on all of those critters at the time, I don't see any
> advantage in simulating them in addition to the existing VAX-11/780.
> Honestly, they were a bit of a pain. The MicroVAXen were much better.
> :-)
>
> Dave
>   



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