New Multi-Threaded Pi Program - Faster than SuperPi and PiFast

[spdycpu]

Hi ,

here a benchmark with a DELL Precision T7400 with 2x Intel Xeon E5420. (non oc, all default)

Why is my performance on a real 8 Core machine so bad in in comparison with a "little Core i7 920 250 Dollar CPU".. ? This is only one physical quadcore? And faster than a 3500 Dollar Dell Precision T7400 ???

I believe this is due to you having the older quad core. It does not have an integrated memory controller like the i7, yours is on the chipset rather than the processor. Also the i7 is triple channel DDR3, I've seen memory reads in excess of 29gb/s. I think the main problem with the Core 2 Quad and the Xeons based off the Core 2 Quad is the older bus. Even a single Core 2 Quad has two dual cores under the heat spreader. For example, Core 0 and 1 is a die, Core 2 and 3 is another. If core 0 and 1 do the work it is quick, if core 0 and 3 do the work the speed is hindered quite a bit due to the traffic still needing to go to the bus. Also since you have two quad cores the bus gets saturated with that kind of traffic, it isn't quite as efficient as the AMD and i7 bus.

Also what helps is the "little" i7 was overclocked from 2.66GHz to 4.4GHz and has the benefit of Hyperthreading. The L3 cache was also overclocked from 2.4GHz to 3.6GHz. My i7 was $199, not too bad of a price/performance ratio I think.