Multiprocessor Qbus PDP-11

[Charles Dickman]

On Fri, Aug 20, 2021 at 7:55 AM Paul Koning <paulkoning at comcast.net> wrote:

>
>
> > On Aug 19, 2021, at 7:39 PM, Charles Dickman via cctalk <
> cctalk at classiccmp.org> wrote:
> >
> > There are indications in the KDJ11-B processor spec on bitsavers that the
> > M8190 could be used in a multiprocessor configuration. For example, bit
> 10
> > of the Maintenance Register (17 777 750) is labeled "Multiprocessor
> Slave"
> > and indicates that the bus arbitrator is disabled.
>


> Interesting.
>
> > Would it be as simple as connecting to 11/83 qbus together? And adding
> the
> > proper software.
>
> I would not think so.  The processor is the bus controller, and you can't
> have a bus with two controllers.  It would be a bit like trying to connect
> a pair of PCs with a PCI or PCIe jumper cable.
>
> To make these configurations work you need a device in between that
> arbitrates the actions of the multiple controllers (PCI people call that a
> "non-transparent bridge").
>
Understood, but the processor spec indicates that it should be possible to
turn off the local arbitrator, so the processor at one end would have its
arbitrator on and the processor at the other end would have the arbitrator
turned off.



>         paul
>
>