Author: Robert Hyatt
Date: 17:13:51 07/08/03
Go up one level in this thread
On July 08, 2003 at 19:42:11, Jeremiah Penery wrote: >On July 08, 2003 at 11:49:39, Robert Hyatt wrote: > >>On July 08, 2003 at 00:33:09, Jeremiah Penery wrote: >> >>>On July 07, 2003 at 23:33:48, Robert Hyatt wrote: >>> >>>>On July 07, 2003 at 11:30:34, Vincent Diepeveen wrote: >>> >>>>>The total bandwidth a 256 node machine with bricks of 4 processors will have >>>>>then a total bandwidth of somewhere around: 12.4 Terabyte a second. >>>>> >>>>>Now *that* is very impressive. >>>> >>>>And imaginary I'll bet. >>> >>>Cray is supposed to be building a 10k processor Opteron supercomputer for Sandia >>>Labs. Its total aggregate bandwidth should far exceed 12.4TB/sec. >> >>Again, that is a theoretical peak, which assumes _all_ processors are >>communicating with each other in such a way there are no conflicts or >>hot spots. The 48 gb/sec for a single T90 CPU doesn't have that kind of >>assumption. > >Of course, for each processor, the bandwidth of a real vector CPU far exceeds >that of any scalar CPU. Have you seen specs for Cray's new X1 stuff? I think I >read something like 200GB/s/processor local memory bandwidth, via 128 RAMBUS >channels or something insane. They have _always_ been "insane" up there. IE how many machines do you know that can have 4096 _banks_ of memory that can all transfer data in parallel? :) Of course, it is also insanely expensive. > >>>>>Especially for the price they will deliver it for. >>>>> >>>>>A 5000 processor vector machine now costs around 700 million dollar. >>>> >>>>Where can you find a "5000 processor vector machine?" >>>> >>>>I know where there is a 32 processor vector machine. Nothing beyond >>>>that that I know of, unless you start counting I860 type boxes. >>> >>>NEC Earth Simulator has 5120 NEC SX-7(?) vector processors. Total cost was less >>>than $400m. >> >>OK. That's a cluster. In that light Cray Research used to have a big cluster >>of YMPs at their headquarters. >> >>I have run Cray Blitz on an SX in the past. >> >>>Here is a blurb about the chip, from the webpage: >>> >>>"Each AP consists of a 4-way super-scalar unit (SU), a vector unit (VU), and >>>main memory access control unit on a single LSI chip. The AP operates at a clock >>>frequency of 500MHz with some circuits operating at 1GHz. Each SU is a >>>super-scalar processor with 64KB instruction caches, 64KB data caches, and 128 >>>general-purpose scalar registers. Branch prediction, data prefetching and >>>out-of-order instruction execution are all employed. Each VU has 72 vector >>>registers, each of which can has 256 vector elements, along with 8 sets of six >>>different types of vector pipelines: addition/shifting, multiplication, >>>division, logical operations, masking, and load/store. The same type of vector >>>pipelines works together by a single vector instruction and pipelines of >>>different types can operate concurrently." >>> >>>Each chip consumes only about 140W, rather than Vincent's assertion of 150KW. >> >> >>The 150KW was for a machine like the C90/T90/etc. 125KW might just get them >>started. :) > >Yeah, the entire Earth Simulator system uses some 7MW of power.
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