AMD Announces Zen 4C Cores Coming To Ryzen Laptops

We've been impressed with AMD Zen 4C cores with their initial appearance in Bergamo with the flagship EPYC 9754 and then over the summer with Siena for the likes of the EPYC 8324P(N) plus the EPYC 8354P(N) review soon. Today AMD is confirming what many had anticipated: Zen 4C cores will be coming to new Ryzen laptop SoCs.

The Zen 4C cores optimized for power efficiency and core density while still delivering great performance will be making their premiere in future Ryzen laptops. Zen 4C cores are 35% smaller than Zen 4.

AMD acknowledges Zen 4C does allow for better scalability for premium with potentially allowing higher core counts than today's laptop core/thread count limits, but for today's announcement is focusing more on the entry-level with allowing smaller cores to provide more options for consumers.

In particular, the Ryzen 3 7440U with its 8 cores / 8 threads will use Zen 4C as well as the new Ryzen 5 7545U to replace the Ryzen 5 7540U. The Ryzen 5 7545U will feature two Zen 4 cores and four Zen 4C cores, compared to the six Zen 4 cores found with the Ryzen 5 7540U. The Zen 4 cores will clock higher than Zen 4C.

Particularly at 15 Watts and lower, the Ryzen 5 7545U delivers better performance than the Ryzen 5 7540U while delivering similar performance at higher power envelopes. The slides do note the new Zen 4+4C SKUs lack Ryzen AI, but for Linux users that isn't really important for now with Ryzen AI not (yet) supported on Linux.

AMD was quick to acknowledge that these aren't "efficiency" cores like with Intel Core hybrid CPU designs. Though they are making use of AMD P-State (ACPI CPPC) Preferred Cores for communicating the Zen 4 vs. Zen 4C cores to the operating system. It's good that AMD Linux engineers have been working on the Preferred Cores functionality for their AMD P-State driver. As of Linux 6.7 the AMD P-State Preferred Cores support hasn't been merged but presumably for Linux 6.8 in early 2024. For now Linux won't make the distinction between Zen 4 and Zen 4C cores, but as seen with Bergamo and Siena testing these cores are very performant and capable, especially with maintaining the same Zen 4 ISA including AVX-512, SMT, and similar features.

With the Zen 4C cores still having AVX-512 and all the same ISA and IPC as Zen 4, this hybrid core design for select Ryzen mobile SKUs is quite fascinating. Having extensively benchmarked Bergamo and Siena processors, Zen 4C is great for power efficiency while still delivering leading performance and increasing core density.

For now they are just talking up Zen 4C in mobile on the entry level side while it will be interesting when AMD gets to introducing the new premium SKUs that will surely be coming for allowing higher core count designs thanks to the smaller footprint of Zen 4C. Those future SKUs should be quite interesting and presumably by that time the AMD Preferred Cores patches for Linux will have been mainlined. Presumably those future premium SKUs will be a mix of Zen 4 and 4C cores, but I also wonder about the prospects of an all-4C high core count option. For laptops / mobile workstations catering to developers in particular where you are often either just running some web browsers, terminal(s) and/or an IDE and prefer the power-savings for those non-demanding workloads but then when it comes to compiling code wanting to leverage high core counts to benefit compiling large code-bases more quickly. In cases like that an all Zen 4C core model would make sense for those developer type workflows. Similarly it will be fascinating to see what comes of Zen 4C for any desktop APUs. In any event the slides provided by AMD in advance were light on benchmarks and other details, but hopefully with time I'll find my hands on some of the new models for some interesting Linux tests.