Monday, October 17th 2022
AMD Ryzen 9 7950X Posts Significantly Higher Gaming Performance with a CCD Disabled
AMD Ryzen 9 7950X 16-core processor exhibits some strange behavior with regards to the max boost frequency spread among its cores. A multi-chip module with two 8-core CCDs (CPU complex dies); we noticed early on in our review that the cores located in CCD-1 boost to a higher frequency than the ones in CCD-2, with differences as high as 300 MHz. CapFrameX noticed that when CCD-2 is disabled on a machine running Windows 11 22H2, the processor actually puts out higher gaming performance, by as much as 10%. This is mainly because the cores in CCD-2, with a lower maximum boost frequency no longer handle processing load from the game; and with CCD-2 disabled, CCD-1 has all of the processor's power budget—up to 230 W—to itself, giving it much higher boost residency across its 8 cores.
Source:
CapFrameX
47 Comments on AMD Ryzen 9 7950X Posts Significantly Higher Gaming Performance with a CCD Disabled
Can avoid some scheduler behaviours by disabling CPPC Preferred Cores on 1CCD CPUs, but for 2CCD it doesn't do much to avoid Windows picking some CCD2 core. The 5800X3D result is not the same.
Uncore in CPU-Z is Fabric FCLK for Ryzens.
L3 runs on its own clock that usually (but not always, especially for X3D) mirrors core clocks. It doesn't share clock domain, nor voltage domain with Fabric.
I thought they already addressed such issues with Zen 3
When you disable 1 CDD on the 7950X does that mean the L3 cache available is 32MB or is it still at 64MB?
1CDD with access to 64MB of L3 should be faster in games??
In September there was and ACPI fix speeding up all AMD arch on linux... TPU doesn't cover those kind of news as it ain't yellow enough.
I like the quote... you don't have to guess who said this.
There's a good reason why CPU-Z describes 2CCD L3 as being 4x16MB (Matisse) or 2x32MB (Vermeer, Raphael), not simply 64MB.
I mean, does the 1 CCD of 7950X has access to much more cache compared to 7700X and 7600X?
There's more energy and effective bandwidth available to the enabled CCD. There's also the fact that the disabled CCD makes zero requests to the system memory.
All this just means that Zen4 non-X3D is probably more bandwidth-limited than anything else, just like Zen3.