VAX Architecture (was KA620)

From: Antonio Carlini <>
Date: Mon Mar 22 13:57:53 2004

> Hmm, did they seek process page tables in physical or in
> system virtual memory? If the latter, I don't see how can
> they be called rtVAX, as that by definition means the former.
> If the former, how can you do that with a standard VAX chip?
> Or does CVAX have an undocumented hack pin which when tied
> opposite to what general specs say causes it to seek process
> page tables in physical memory?

I think that the chip used in the KA620 was the only modified
VAX chip - the other rtVAX machines were AFAIK based on real
CVAX chips. I don't think that there was ever a formal
definition of rtVAX: it was just a way of selling a VAX-like
chpi in the early days that would not run VMS but would run
VAXeln or a customer's own OS. Later on I guess someone decided
the whole thing was a silly waste of time and it was easier to
sell unmodified chips on an rtVAX board rather than waste effort
producing a CVAX variant.

> STD 032 for completeness, but this task can be left until
> later when we can raise a large enough army (using human
> cloning, genetic eng. and neurolinguistic programming to make
> perfect killing-machine soldiers) to invade and overrun USA
> including ex-DEC facilities and archives.

I heard the archives (or what was left of them) headed off to
the Computer Museum in Boston. Anything left now is just sitting
in someone's cupboard rather than in a central repository.

> So this only leaves SID codes 0x0C, 0x0D and 0x0F as
> unexplained gaps. I suppose that perhaps 0x0F could have

I know at least one VAX never made it out: it was called
Ravne and was (probably) an ECL-based machine. You now
know as much about it as I do! I expect that there must
have been other abandoned projects.

> One reason it's important to understand the complete history
> of SID code assignments is that if we start building new
> VAXen, we'll need a new SID code registry. I plan on calling

I think that both Alpha and MIPs had SID assignments. I think
Alpha was 1024 and above, MIPs was 128 and above (but presumably
below 127). So if you pick 126 and work downwards you should
be safe :-) Good luck finding documentation for this: it's
just something I think I vaguely remember.

> Interestingly, however, it appears that at some point there
> were diagnostic programs available to the general public
> that, judging from the descriptions, apparently do similar
> instruction testing, though they were presumably intended for
> troubleshooting broken hardware rather than for validating
> new implementations. The KA820 Technical Manual, for
> example, refers to these:

There were machine-specific and peripheral-specific
diagnostic tools used by Field Service. I expect self-
maintenance customers cuold have had access to these.
I've never come across any of these diags but the
best place to find them would be ebay or an ex-FS
engineer. Whether the diags would still be readable
is another matter!

Antonio Carlini   
Received on Mon Mar 22 2004 - 13:57:53 GMT

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