Haven hashrate problem with AMD Zen 3 "Cezanne"
Hi,

regular Zen 3 "Vermeer" based Ryzen 5000, e.g. Ryzen 5 5600X, work fine with Haven algo cn/xhv. They are hashing around 700 H/s (single CCD).

But there is another Zen 3 model out there, the Ryzen 5 5600G "Cezanne". It has an iGPU (which isn't used here so doesn't matter) and just 16 MB L3 cache instead of 32 MB. So Cezanne can only start 4 threads mining cn/xhv because of the scratchpad size (4 MB) of that algo (16 MB / 4 MB per thread = 4 threads).

That's ok and is the same as the older Zen 1 type CPUs like Ryzen 5 1600. But those old CPU are capable of hashing over 200 H/s with Haven. Cezanne instead is stuck at under 90 H/s. So there's something wrong.
![haven-cezanne](https://user-images.githubusercontent.com/60088495/141209693-083f6402-8704-4b94-bd4e-9df39e319380.png)

Other algos like Monero (rx/0; 5500 H/s) or Dero (astrobwt; 875 H/s) are behaving normal on Cezanne, the hashrates are where you would expect them for arc, threads, clock frequency and L3 cache. It's just cn/xhv which is way too slow.

How can I help debugging?