Quote from: kyndik on May 05, 2014, 08:44:34 AM

rdebourbon, Hi!
Could you please explain why AMD FX-4300 @ 4.3GHz (-t 4, MNPS=280) slower then AMD Athlon II 280 @ 3.6Ghz (-t 2, MNPS=297). Tried on jhPrimeminer_RdBBeta4.0J_x64 for Athlon;
jhPrimeminer_RdBBeta4.0J_x64-AVX and jhPrimeminer_RdBBeta4.0J_x64 for FX-4300
OS: Fresh Windows 8.1 x64

Thank you in advance.

Without doing more exhaustive tests I couldn't say for certain, but I suspect the issue will be on-die cache differences within the CPUs..

A quick look at CPU-World (I didn't go any further so data could be wrong) indicates that despite the higher core count, the L1 data cache is smaller (half the size!) on the FX-4300 compared to the Athlon II..

FX-4300:
2 x 64 KB 2-way set associative shared instruction caches
4 x 16 KB 4-way set associative data caches

Athlon II 280:
2 x 64 KB 2-way set associative instruction caches
2 x 64 KB 2-way set associative data caches

If this is true, it will result in a higher L1 miss ratio - which could account for the performance difference. Having said all that, I'd be a bit surprised if that was the sole reason for a such a drastic difference in performance..