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

[Mechromancer]

this has to do with bottlenecks in the cpu. AMD has very fast execution units but slow retirement units and performs well under full load. the predecoding in core 2 limits performance in cpu intensive programs.

I was thinking the exact opposite. Core 2 has better SSE throughput than K10, but Core 2 is limited by memory bandwidth.

Now for a quick disclaimer on yet-another "sensitive" issue of Intel vs. AMD:
Before anybody yells at me for drawing a conclusion that Intel has faster arithmetic than AMD, this is merely my guesstimate based on the benchmarks. In no way does it indicate that Intel or AMD is better.
Since the vast majority of the program was written and tuned on Pentium and Harpertown (which is a Core 2), I'd expect there so be some favoring towards Intel.

As for the memory bandwidth issue, I've noticed that the program scales pretty poorly on Core 2 Quads... But, the only ones I've played with is Q6600 and Q9400 - both of which have significantly smaller cache than Harpertown.


If we to want throw out the bandwidth factor to determine which (Core 2 or K10) has better arithmetic throughput for this program, we'll need to do a single-threaded benchmark comparison between a Core 2 and a K10 at the same frequency.

My guess is that Core 2 will win (simply because I tuned for it), but I unfortunately don't have access to any K10s to try it.


Anyone have both and care enough to try that?

Don't worry about saying one performs better than the other. The truth is both AMD and Intel uarchs have their strengths and weaknesses. If they were both good and bad at the same tasks and performed exactly the same it would make for a pretty boring conversation. Differences are good for this reason.

@Poke and Chumbucket: You two come to different conclusions as to where the performance and bottlenecks are on each platform. I suggest that you may both be correct. AMD has a great HyperTransport platform to work with, and needs to be pused at full load to shine. Core 2 gets choked up under load because of Chumbuckets' explanation and FSB bandwidth anemia.

PS: Dropping my memory from 1066 to 800 only increased my 25M score by less than 0.3 seconds. Not as bad of a hit as I was expecting.

EDIT: Single Threaded Phenom II 25M Test