Multi-CPU Qbus VAXen

From: Antonio Carlini <arcarlini_at_iee.org>
Date: Fri Oct 10 16:47:05 2003

> AFAIK, the KA650 and KA655 do not have the support for
> multiple processors on Qbus that was present in the KA630.
> The KA630 (MicroVAX II) had two features for this:
>
> 1) The bus interface could be configured to be a bus requester rather
> than the system bus arbiter. This has to be done on all CPUs
other
> than the first. (Note that the VAX 11/780 was also capable of
this,
> as discovered and exploited by George Goble).

It may be, as you say, that the KA65x cannot do this. The KA655 TM seems
to be silent here - or at least it is in the sections I quickly read
just
now. The bus interface is handled by the CQBIC, but I don't have that
particular manual handy right now. If the CQBIC can do this, then I
expect
that most of the CVAX MicroVAX 3000 Series machines can do it (and if it
cannot, then presumably none of them can).

> 2) Each processor has a "doorbell" register to allow other processors
> to interrupt it.

This I think it does have - at least it has a register called IPCR. I
don't
have the KA630 User Guide (*sniff* - someone must have one they can
scan!)
so I cannot compare terminology directly, but I think this is what the
doorbell register is. Since I don't know of anything that uses it,
finding
example code to verify this may be somewhat hard!
 
-- 
---------------
Antonio Carlini             arcarlini_at_iee.org 
Received on Fri Oct 10 2003 - 16:47:05 BST

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