How to derive the Peak performance in GFlop/s of Intel Xeon E5-2690?

Question

I was able to find the theoretical DP peak performance 371 GFlop/s for the Xeon E5-2690 in this Processor Comparison (interesting that it is easier to find this information in Intel's competitor than Intel support pages itself). However, when I try to derive that peak performance my derivation doesn't match:

1. The frequency (in Turbo mode) for each core of the Xeon E5-2690 = 3.8Ghz
2. The processor can do an add and mul operation per cycle so we get: 3.8 x 2 = 7.6
3. Given it has AVX support it can do 4 double operations per cycle: 7.6 x 4 = 30.4
4. Finally, it has 8 cores, therefore we get: 8 x 30.4 = 243.2

Thus, the peak performance in Gflop/s would be 243.2 GFlop/s and not 371 GFlop/s?

Cushitic

Where did you find the Information that this processor can do an ADD and MUL Operation in one cycle? Is this the Fused Multiply Add (FMA) technique? – Phyllode

Answer 1

Turbo Mode is not used to calculate Theoretical Peak Performance, you have to consider something like:

CPU speed = 2.9 GHz

CPU Cores = 8

CPU instruction per cycle = 8 (considering AVX-256 -> 256 bits unit, can hold 8 single precision values) x 2 (add and mul operations like you said) = 16

Putting all together:

2.9x8x16 = 371 GFlops/s

Potshot

It is very important then to point out that you calculated the SINGLE precision Theoretical Peak while my calculation is +/- correct for computing the DOUBLE precision Theoretical Peak except the Turbo mode point and using 2.9 Ghz as you mentioned. – Cushitic

Turbo Mode is not normally applicable when using all CPU cores. With AVX max DP GFLOPS would be 185.5. – Alexander

Flops = floating operations per second – Punchy