AMD’s latest AGESA firmware bugs out certain Ryzen 5 processors, disabling a couple of cores upon booting into Windows. AGESA ComboAM5PI 18.104.22.168 was rolled out early last month to improve boot times. Unfortunately, it worsened multi-threaded performance by disabling one to two cores on Ryzen 5 7600X processors leveraging a dual-CCD design.
AMD has been repurposing dual-CCD chips initially meant for Ryzen 9 SKUs to power the hex and octa-core Ryzen 5/Ryzen 7 CPUs by disabling the additional cores. Usually, the lower-end offerings are derived from single CCD designs, with the higher-end parts leveraging dual-CCD implementations. Silicon yields are never perfect, forcing vendors to reuse discarded higher-end dies for budget offerings.
The result? You get hex-core CPUs based on two eight-core CCDs, both partly disabled. This can improve the thermal performance of the processor but also worsen the inter-core latency between the cores on the disaggregated dies. Either way, it looks like the latest AGESA firmware is having difficulty distinguishing between the two implementations of the hex-core Ryzen 5 SKU.