Multiprocessor Qbus PDP-11

Paul Koning paulkoning at
Fri Aug 20 06:55:16 CDT 2021

> On Aug 19, 2021, at 7:39 PM, Charles Dickman via cctalk <cctalk at> 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. There is also section
> 6.6, "Cache Multi-Processor Hooks", that describes cache features that
> allow multiprocessor operation.


> 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").  


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