What CPU to use for ABC, and why?

[Dirk Broer]

The Project
The ABC conjecture involves abc-triples: positive integers a,b,c such that a+b=c, a < b < c, a,b,c have no common divisors and c > rad(abc), the so-called radical of abc. The ABC conjecture says that there are only finitely many a,b,c such that log(c)/log(rad(abc)) > h for any real h > 1. The ABC conjecture is currently one of the greatest open problems in mathematics. If it is proven to be true, a lot of other open problems can be answered directly from it. ABC favores 64-bit OS and CPUs

The Applications
Linux/x86 2.10
Linux/x86_64-pc 2.10
Linux/32-bit PowerPC
Mac OS X (Intel) 2.10
Mac OS X (Intel 64-bit) 2.10
Mac OS X (PowerPC) 2.10
Windows/x86 2.10
Windows/x86_64 2.10

There seem to be no optimized clients that make the best use of the various instruction sets that have been added to CPUs over time.

The Stats
Recent top-5 best scoring computers used:
Opteron 6172 (4x12=48 cores)
Xeon X5680 (2x6 cores, 24 threads)
i7-980 (6-core, 12 threads)
Xeon E5520 (2x4 cores, 16 threads)
i7-2600K (4-core, 8 threads)

ABC sure likes you to bring in as much cores as you can support. I'd like to know what a quartet of Opteron 6282SE's would do...That's 64 cores!

All-time top-5 best scoring computers used:
Xeon X7350 (4x4=16 cores)
Xeon E5440 (4 cores, 8 threads)
Xeon X5470 (2x4=8 cores)
i7-860 (4 cores, 8 threads)
Xeon E5520 (2x4 cores, 16 threads)

WUProp comes with a table showing credit per core per day showing that, while the 8-core FX-8150 Bulldozers do not have the highest scores per core per day, their 8 cores will guarantee a score per CPU per day in the top of the field. Bulldozer is about the level of the Phenom II per core and only slightly worse than the i5 and i7. Overclocking does not help, according to WUProp.

Highest scores per core per day are for the i5-2500K, using 64-bit Linux. This OS scores significantly higher for this CPU per core per day, around 2500 compared to 1500 for Windows.

Best performing AMD CPU -per core- is the AMD Phenom II X6 1090T (6 cores, using an OC of 20% to 30%), but 6x 1340 is still less than 8x 1136, so Bulldozer FX-8150 wins the AMD contest. There are no Bulldozers using 64-bit Linux in the database of WUProp yet.