256 Threads in a 4U box.
According to Fowler, the four-socket variant of the “Victoria Falls” Sparc T2+ processor is “imminent to ship”. This processor first appeared in two-socket “Niagara” class servers, code-named Maramba, back in early April.
To make the Sparc T2+ chip, Sun took a Sparc T2 chip and took out two on-chip memory controllers and the integrated “Neptune” 10 Gigabit Ethernet ports. It replaced them with symmetric multiprocessing links that use some of the memory lanes on the processor to lash the two caches in the chips together into a two-way processor complex. Each Sparc T2 and T2+ chip has eight Sparc cores, with eight threads each, for a total of 64 threads.
Cores run at 1.2 GHz or 1.4 GHz. With the four-socket Victoria Falls machine, Sun will be able to put 256 threads in a 4U box purportedly code-named “Botaka”. The four processors in this impending server do not link together gluelessly (as they did in the two-socket box using T2 chips), but rather are connected through a crossbar switch named “Zambezi”.
And once you have a crossbar switch, of course, there is no reason to stop at four sockets – and perhaps Sun won’t. Fowler is not saying, and sources at Sun speaking earlier this year said larger T2+ boxes were not on the way.