Computer System Having Multiple Computer Devices Each with Routing Logic and Memory Controller and Multiple Computer Devices Each with Processing Circuitry

A computer comprising:

• a first computer device of a first class;
• a second computer device of the first class, each computer device of the first class comprising a first external port and a second external port, at least one memory controller configured to attach to external memory, and routing logic configurable to route data from the first external port to one of the at least one memory controller and the second external port;
• a third computer device of a second class, the third computer device being connected to the first external ports via first and second links, the third computer device comprising first processing circuitry configured to execute a first computer program and connected to the first and second links to transmit and receive messages;
• and
• a fourth computer device of the second class, the fourth computer device being connected to the second external ports via third and fourth links, the fourth computer device comprising second processing circuitry configured to execute a second computer program and connected to the third and fourth links to transmit and receive messages.