[hashcash] Re: stamp speeds on new hardware

Adam Back wrote: 
bas sent me a 40-bit stamp... nice:

        1:40:051210:beware@xxxxxxxxx::qsCVFGF+ZkcA/B63:SNSrr

took 28 hours on the pair of below machines with 2 cores used on the
athlon64 x2.  (I think the p4 prescott 3.6Ghz does not have
hyperthreading).

it has HT but i don't enable it.


The stats for those machines:

        http://www.hashcash.org/benchmark/

4.68 Mh/s       0.22s   2.2Ghz  athlon64 x2     mmx std 1x2

3.9 Mh/s        0.27s   3.6Ghz  P4 prescott     mmx std 1x2

That is one core on the athlon64 so a single athlon64 x2 with both
cores slightly outperforms the 2Ghz G5.

But I would think assembler targetted at the 64 bit athlon + any 64
bit mmx / sse variant should get a boost on a 64bit vs 32bit athlon?

Adam


the used asm is i386, with mmx. it doesnt take advantage of the amd64 instruction set (if it did, this same code wouldnt be i386 compatible).
while mmx is 64 bits, this is entirely a different 64 bits than amd64, and available on any mmx supporting cpu. you can calculate:

athlon64: 4.68 / 2.2 = 2.13 Mh/s/GHz
athlon XP: 3.4 / 2.18 = 1.56 Mh/s/GHz

same code, same clock speed, different Mh/s/clock speed. this is because of the athlon64's improvements over the XP: a more complicated design with much more transistors, improved branch prediction, improved dependency/parallellization detection, more execution units, more cache, etc. this is not because of amd64 opcodes: in fact the cpu is not fully utilized.
this is exactly the opposite of what intel does: the prescott has less efficiency per clock compared to the northwood (the precious p4), in favor of a higher clock speed.

amd64 assembler is likely to be faster and give more room for optimization tricks, but it requires an amd64 OS such as windows XP 64 bits.


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