HyperTransport

From PEL Wiki

Bus Basics

HyperTransport is a low-latency packetized bus designed by AMD as Lightning Data Transport (LDT) and pushed by the HyperTransport Consortium It allows glueless multiprocessing for AMD Opteron processors up to 8-way.

HTX is the specification for the HyperTransport expansion card. One company makes an HTX Infiniband card, which allows high performance clusters to be built.

HyperTransport 2.0 can be up to 32 bits wide and it is DDR up to 1.4 GHz. The Opterons I have have 16-bit wide, 800 MHz buses, for 800 * 2 (DDR) * 2 (Bytes wide) * 2 (links) 6.4 GB/sec total bandwidth (3.2 GB/sec each direction).

Torrenza

AMD announced an initiative to open up their coherent HyperTransport to enable move coprocessors. Sun, HP, Cray, and others have reportedly signed up.