AMD Zen 3 at Hot Chips 33

AMD has a talk at Hot Chips 33. During this talk, the topic was the AMD “Next Generation “Zen 3″ Core”. We will quickly note that AMD is really discussing its current generation core powering the AMD Ryzen 5000 series and more pertinent to STH, the AMD EPYC 7003 series. If you want to learn more about Zen 3, you can see either of those pieces. Since we have covered Zen 3 a lot at STH, we wanted to instead focus on some of the Hot Chips 33 (2021) newer items looking at the future. We are updating this live so please excuse typos.

AMD Zen 3 at Hot Chips 33

AMD first focused on the fact that it has released three architectures with >10% IPC uplift. Zen/ Zen+ was the huge step function but 19% IPC is still a large number.

One of the key innovations for Zen 3 was its cache hierarchy. Especially on the server-side with the EPYC 7002 “Rome” to EPYC 7003 “Milan” transition, the shift to a unified L3 cache on each compute die was a major performance improvement. Something we do know is that Intel is pushing the capacity of its L2 cache in its next-generation so we have a feeling that Zen 4 will need more cache innovation.

We covered this recently in our Server CPUs Transitioning to the GB Onboard Era. The first 3D package that AMD discussed was a Zen3 based compute die (CCD) with its normal 32MB of L3 cache but with 64MB of L3 cache added to each CCD for 96 per CCD and 192MB L3 cache total.

We recently covered Intel Details Sapphire Rapids Xeon adding HBM stacks. AMD is aware of this and we expect them to announce a response. That will usher in the GB era of onboard memory.

At Hot Chips 33, AMD reiterated that TSMC 5nm Zen4 is on track. We expect to see it in servers in 2022 but the chip supply challenges are not minimal.

Overall, AMD is showing innovation cycles that are a bit over a year long. This slide is a bit of a market knock on Intel that had its Skylake architecture stagnating the industry for years due to Intel’s 10nm challenges.

Final Words

For STH readers, the talk was mostly a history lesson rather than a look at a next-generation part. We are excited for Zen 4 and some of AMD’s next-generation technologies. We just wish that AMD was a bit more forthcoming as Intel has been. Let us just say there is probably a business reason behind this. Intel needs to re-ignite interest in its products through promises of a next-generation. AMD is probably supply-constrained to the point that it does not want to cause delays from announcing the next generation too early. We will simply say that 2022 processors will make 2021 processors look quaint.