[Coco] hardware port mapping question

[Mike Pepe]

Mark McDougall wrote:

> Mike Pepe wrote:

> 

>> Essentially what you're making here could be a 4x4 crossbar switch:

>>

>>  ABCD

>> A++++

>> B++++

>> C++++

>> D++++

>>

>> It could be done with a bunch of latches and tri-state buffers. 

>> Arbitration could be an issue, but it sounds like what you're looking 

>> for is for each CoCo to have one "out" port that can be read by the 

>> others. If that's the case, it becomes more possible. If you're 

>> looking to write values into a common register, it becomes much more 

>> complex.

> 

> You could, of course, come up with a protocol that requires each 

> computer to write to its own latch only.

> 

> Regards,

> 


Yes, it could be very simple- here's what I'm thinking.

Each CoCo has one "Out" port, which can be read by all machines, say at 
a different address.

Each CoCo would poll the others for messages, reading twice to ensure 
that the data wasn't captured in mid-write, and can respond via its own 
write port.

There would need absolutely need to be some sort of protocol involved to 
co-ordinate this operation.

Is Roger planning on making a multinode supercomputing cluster out of 
CoCos?

-Mike