• Welcome to Overclockers Forums! Join us to reply in threads, receive reduced ads, and to customize your site experience!

Relative IPC in Prime95 of recent CPU generations

Overclockers is supported by our readers. When you click a link to make a purchase, we may earn a commission. Learn More.


Mar 7, 2008
With Zen 5 being teased by AMD it is still unclear what performance it could bring. The rumour it had improved FPU can't be confirmed or denied with current public information. It made me think, I never benchmarked Zen 4 which I recently got myself, and compare it to Intel offerings with and without AVX-512 support. Note I didn't tightly control clocks so there may be a few % error margin potential.

Relative Prime95 IPC with AVX2 and AVX-512 when not memory bound, normalised to Skylake AVX2 = 100%.

Skylake-X: 100%, 173%
Rocket Lake: 128%, 143%
Alder Lake: 139%, not supported
Zen 4: 131%, 152%

From past testing, I knew Rocket Lake was about +40% and Skylake-X was about +80% relative to Skylake. It is good this latest testing remains in that ball park.
What I didn't look at previously was AVX2 performance uplift, which is greater than I thought. Alder Lake AVX2 performance is near enough same as Rocket Lake AVX-512 performance and even takes the lead over Zen 4.

Looking at the improvement AVX-512 brings within the same architecture we get:
Skylake-X: +73%
Rocket Lake: +12%
Zen 4: +16%

Skylake-X does have double the FP execution resource compared to most, so that likely helps enable the bigger improvement. Rocket Lake and Zen 4 don't benefit from having extra FPU resource, so the improvements there may be down to other AVX-512 instructions, particularly those relating to reorganising data. The combination with other microarchitecture improvements helps uplift the overall performance compared to earlier architectures.

It would be interesting to see where Sapphire Rapids would sit in all this as Intel's current best, but it is way out of my price range.

I'll keep an eye on the news to see where Zen 5 might end up.


Upgrade to 512-bit FPU execution confirmed. This to me is the big perf news. This should give AMD leadership in that area over Intel too, although we'll still need more details and testing to confirm.
Last edited: