A Three-Way AMD Opteron Server

Abdul tips a thin little review up at The Inquirer of the Themis Slice. "The Slice is a three socket Opteron machine with two PCIe slots and two Infiniband 4x ports... Why would you want three sockets rather than four? Easy, latency. Any CPU in a 3S system is one hop away from any other CPU. In a 4S system, you can be two hops away. This adds latency, and more importantly, you take a big hit on cache coherency latency. This kills performance."

Comments

CoProcessors?

[tji]

Wasn't AMD also talking about licenses or agreements with other companies to allow for different types of coprocessor chips to be used alongside their processors?

There is some interesting potential in that realm.. Crypto accelerators for VPN, SAN, or other devices. Multimedia encode/decode accelerators (encode 1080P H.264 in real time?). Inevitable video game acceleration devices (physics co-processor, accelerated NIC chip, 3D GPU offload processor?).

Those would be even more interesting in home-user oriented Athlon64 boards. Multi-socket opteron boards are out of my price range.

Same latency with 4 processors

[Laxator2]

The article states that with 3 processors one gets better performance, latency wise, because in a triangle configuration any processor cache is just one hop away. You can have 4 processors in a tetrahedron configuration and still have any processor one hop away. Of course it will take 3 hypertransport connections per processor just for the internal communications, so a 4th connection is needed for at least one processor to connect to the northbridge. The quad-core Opteron will have a maximum of 4 hypertransport connections, is that right ?