multiprocessor microPDP-11/83

Eric Smith eric at
Wed Jul 23 18:35:48 CDT 2008

Charles H Dickman wrote:
> Is it possible to connect the Qbus of two 
> microPDP-11/83s together? what about Unibus PDP-11/84s?

Neither one without a lot of hardware hacking.

> Since bus arbitration is handled by the processor, arbitration on one of 
> the processors would need to be disabled. The KDJ11-B Users Guide 
> doesn't suggest a way to do this.

AFAIK, there's no feature to do that designed into it.

IIRC, the MicroVAX II CPU module (KA630) was designed to do exactly what 
you describe.

> I am tired of reading about the first computer on the internet... 

I haven't seen any discussion of that here, and it's not controversial.

> Besides, I have not heard any of you wise guys argue that there couldn't 
> be a first computer on the internet (or Internet) or any network since a 
> single computer can't make up a network.

Well, one of them had to be the first to send a packet, and I think you 
can argue that you are connected to the internet until you actually send 
or receive a packet.  The node receiving that first packet would then be 
the second node on the internet, since it started receiving the packet 
at a later time than the first node started sending it (due to 
propogation delay).


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