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
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