Vincent, Ah, thanks; I was neglecting ops per cycle variations among cores. Peter
On Nov 9, 2007 12:21 PM, Vincent Diepeveen <[EMAIL PROTECTED]> wrote: > Ok easy theoretic calculation, and it's still very rude of course: > > 1 core 2.4Ghz * 3 instructions a cycle * (sse)2 = 7.2 * 2 = 14.4 Gflop > 4 cores of a quad core ==> 57.6 gflop > 3 nodes ==> 3 * 57.6 = 172.8 gflop > > Now of course your software won't be able to get that out of the > hardware at core2, > at new K8 cores perhaps it goes a tad better (though they aren't > there yet). > > More careful calculation for core2 you can do using 2 instructions a > cycle: > > 172.8 * 2 / 3 = 115.2 gflop > > If you really want to build this cheapo, checkout pricewatch. I'm > sure one of you can manage it for $1000. > > On other hand at sycortex.com under 'news' i see a 72 cpu solution, > which in their case is 72Gflop (hope i'm wrong) > offered for under $15k. > > Let's say roughly a factor 5-10 difference in price compared to pc's > even if we add power for the coming 3 years? > > Thanks, > Vincent > > > On Nov 9, 2007, at 5:58 PM, Peter St. John wrote: > > > Vincent, > > I'm missing something in the arithmetic. "3 nodes of quadcore" is 12 > > cores? delivering 100 "GFlops" would require something like 8 GHz? So > > perhaps you mean, 3 nodes of dual socket, quadcore CPU (24 cores) at > > 4GHz? And you can get that for $1500? > > Thanks, > > Peter > > > > On Nov 9, 2007 11:44 AM, Vincent Diepeveen <[EMAIL PROTECTED]> wrote: > >> Larry, all what you write is very interesting and of course i hope > >> for you your product line gets a big succes. > >> Just like IBM's blue gene, the major expertise of your product line > >> is that it is only interesting to governments who need major > >> amounts of > >> crunching power (the other conditions left aside such as no big RAM > >> requirements as that usually means you need good branch prediction > >> and so on), > >> and who have million dollar budgets, and probably have a program > >> lying around where this hardware can get used for. > >> > >> The price of a box with say 100 "1 gflop" cpu's, delivering in total > >> 100 gflop isn't gonna be $1500 i guess, whereas for 1500$ one can > >> build hands down > >> 3 nodes with a quadcore, delivering not only *more* than 100 gflop, > >> but also capable of doing other software than just crunching; it's > >> also possible to put > >> a lot of RAM inside and it's also possible to run software that's > >> making a lot of use from the branch predictor. > >> > >> For sure you're not qualifying for a $2500 setup, and with those > >> freak qualifications you qualify bigtime for this mailing list of > >> course :) > >> > >> > >> On Nov 9, 2007, at 3:42 PM, Larry Stewart wrote: > >> > >>> Robert G. Brown wrote: > >>> > >>>> On Thu, 8 Nov 2007, Jim Lux wrote: > >>>> > >>>>> In general, a N GHz processor will be poorer in a flops/Watt > >>>>> sense than a 2N GHz processor. > >>>> > >>> Well that just isn't so. It seems pretty clear from IBMs BlueGene/ > >>> L, as well as the SiCortex processors, that the > >>> opposite is true. The new Green 500 list is brand new, and there's > >>> not much on it yet, but the BG/L is delivering 190MF/Watt > >>> on HPL, whereas the machines made out of Intel and AMD chips are > >>> half that at best. > >>> > >>>>> > >>>>> The power draw is a combination of a fixed load plus a frequency > >>>>> dependent load, so for the SAME processor, running it at N/2 GHz > >>>>> consumes more than 50% of the power of running it at N GHz. > >>>> > >>> This probably IS true, but high performance cores have a lot more > >>> logic in them to try to achieve performance: out of order > >>> execution, complex branch prediction, register renaming, etc. etc. > >>> A slower core can be a lot simpler with the same silicon process, > >>> so a decent lower-clock design will be more power efficient than a > >>> fast clock design. > >>> > >>>>> > >>>>> If you go to a faster processor design, the frequency dependent > >>>>> load gets smaller (smaller feature sizes= smaller capacitance to > >>>>> charge and discharge on each transition). The core voltage is > >>>>> also usually smaller on higher speed processors, which also > >>>>> reduces the power dissipation (smaller number of joules to change > >>>>> the voltage from zero to one or vice versa). So, in general, a > >>>>> 2N GHz processor consumes less than twice the power of a N GHz > >>>>> processor. > >>>> > >>> The flaw in this argument is that a slower clock design can use the > >>> same small transistors and the same current state of the art > >>> processes and it will use many fewer transistors to get its work > >>> done, thus using very much less power. Our 1 GF core is 600 > >>> milliwatts, for example. > >>> Even after adding all the non-core stuff - caches, memory > >>> controllers, interconnect, main memory, and all overhead, it is > >>> still around 3 watts per GF. > >>> > >>>> > >>>> In ADDITION to this is the fact that the processor has to live in a > >>>> house of some sort, and the house itself adds per processor > >>>> overhead. > >>>> This overhead is significant -- typically a minimum of 10-20 W, > >>>> sometimes as much as 30-40 (depending on how many disks you > >>>> have, how > >>> > >>> This factor does not scale this way! With low power processors, > >>> you can pack them together, without the endless support chips, you > >>> can use low power inter-chip signalling, you can use high > >>> efficiency power supplies with their economies of scale. If you > >>> look inside > >>> a PC there are two blocks doing useful work - memory and CPUs, and > >>> a whole board full of useless crap. Look inside a machine designed > >>> to be a cluster and there should be nothing there but cpus and > >>> memory. > >>> > >>> > >>> -- > >>> -Larry / Sector IX > >>> > >>> _______________________________________________ > >>> Beowulf mailing list, Beowulf@beowulf.org > >>> To change your subscription (digest mode or unsubscribe) visit > >>> http://www.beowulf.org/mailman/listinfo/beowulf > >>> > >> > >> _______________________________________________ > >> Beowulf mailing list, Beowulf@beowulf.org > >> To change your subscription (digest mode or unsubscribe) visit > >> http://www.beowulf.org/mailman/listinfo/beowulf > >> > > > > _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
