Processor topology switches

1. A method comprising:

changing switch configurations to change an inter-processor communications topology based on received switch settings switch settings that determine a number of blades to be joined together as a single server in a blade enclosure; and

communicating between processors peer-to-peer via the changed switches.

2. A method as recited in claim 1 wherein said changing involves configuring a switch coupled to a first processor and selectively coupled to switches coupled to second and third processors respectively.

3. A method as recited in claim 2 wherein said configuring involves switching between a single 8-way parallel processor-communications topology and a dual 4-way parallel processor communications topology.

4. A system comprising:

a first processor having a first first-processor port for peer-to-peer processor communications; and

at least a portion of a first-to-second-processor communications path for directing said communication so that they are between said first processor and a second processor;

at least a portion of a first-to-third-processor communication path for directing said communications so that they are between said first processor and a third processor; and

a first switch providing for switching said communications from said first-to-second processor communications path to said first-to-third processor communications path and vice versa, the first switch to switch said communications according to received switch settings that determine a number of blades to be joined together as a single server in a blade enclosure.

5. A system as recited in claim 4 wherein said first switch is an optical switch optically coupled to said first port and to said communications paths.

6. A system as recited in claim 4 wherein said first switch is an electro-optical switch, electrically coupled to said first port and optically coupled to said communications paths.

7. A system as recited in claim 4 wherein said communications paths each include one bi-directional channel.

8. A system as recited in claim 4 wherein said communications paths each include an out-going channel and an incoming channel.

9. A system as recited in claim 4 comprising:

at least eight processors including said first, second, and third processors;

at least eight switches coupled to respective ones of said eight processors; and

one or more switch controllers for controlling said switches so as to alternatively arrange said processors in an 8-way parallel two- or three-hop topology and a dual 4-way one-hop topology.

10. A system as recited in claim 4 further comprising a computing module, said module including said first processor, a first switch of said switches, and at least portions of each of said communications paths.

11. A system as recited in claim 10 wherein said module does not include said second processor and does not include said third processor.

12. A system as recited in claim 10 wherein said module includes a fourth processor and a first-to-fourth-processor communications path, said fourth processor having a first fourth-processor port coupled to said first-to-fourth-processor communications path, said first processor including a second first-processor port coupled to said first-to-fourth-processor communications path for peer-to-peer communications between said first and fourth processors.

13. A system as recited in claim 12 wherein said first-to-fourth-processor communications path is electrical and said portions of said first-to-third-processor communications path and said first-to-third-processor communications path are optical.

14. A system as recited in claim 4 further comprising:

a blade enclosure;

at least four blades installed in said enclosure, each of said blades including at least two processors, said first, second, and third processors being in different respective ones of said blades;

processor switches, including said first processor switch, respectively coupled to said processors;

wherein said processor switches can be alternatively configured to define an 8-way parallel processor topology and a dual 4-way parallel processor topology.

15. A system as recited in claim 14 wherein each of said processors has at least three peer-to-peer processor ports, at least one of the three being coupled to one of said processor switches, said 8-way parallel processor topology being a 2-hop or 3-hop topology, said 4-way parallel processor topology being a one-hop topology.

16. A system as recited in claim 15 wherein each of said processors has one optical peer-to-peer port optically coupled to one of said switches and at least two electrical peer-to-peer ports.

17. A system as recited in claim 15 wherein each of said switches is an electro-optical switch electrically coupled to its respective processor and optically coupled to at least two optical communications paths.