I have a (perhaps silly) hope that AMD is working on a radically new core and doesn't want the details to be public yet (thus also no patents).
I refuse to believe that AMD's long-term plan is to keep iterating Zen forever at the pace of "5-10% IPC improvements every 2 years," especially considering what is already public knowledge. The insiders must be much more aware of industry trends.
There are two main reasons supporting my belief:
1. Let's look at what the competition is doing:
- Qualcomm has a rather agressive roadmap that will definitely outpace "5-10% IPC in 2 years" designs for several generations to come (as they have plenty of low-hanging fruit to pick)
- Apple's M1 is already 5 years old, M4 shows that wide designs can achive good clock speeds. In low-power environments it has an almost silly fficeny edge when running flat out (4.4 vs 5.1 GHz)
- While cancelled, Intel's Royal Core was a significat redesign in the pipeline for Intel (rumored 2X IPC in some cases though with terrible area efficency). Now the same architects are developing something something likely equally radical at Ahead Computing
- While it may end up not delivering, Tenstorrent is planning to release a massive 16-wide clustered RISC-V design in 2-3 years
Some of these parts will not pan out, but most represent more aggressive approaches than slow iterations on existing cores every 20 months More importantly,
none of these developments are new. Royal Core was a known entity for years before cancellation. It would be a terrible strategy for AMD to simply assume "Intel will screw up" and allow themselves to stagnate. Only the paranoid survive, and AMD needs to have a ground-up redesign in their pipeline as a contingency.
2. . Zen Architecture's Maturity
Despite considerable changes in Zen 5, the Zen microarchitecture
is just getting long in the tooth. Here's how often AMD has started from scratch (first level indicates new designs, second level shows iterations):
- K5 - 1996
- K6 - 1997
- K7 (Athlon) - 1999
- K8 (Athlon 64) - 2003
- Bulldozer - 2011
- Piledriver - 2012
- Steamroller - 2014
- Excavator - 2015
- Zen - 2017
- Zen 2 - 2019
- Zen 3 - 2020
- Zen 4 - 2022
- Zen 5 - 2024
- Zen 6 - 2026
Granted, there are major low-level changes in Zen 3 and Zen 5 finally made considerable high-level improvements, but these are nowhere near the comprehensive redesigns seen with Bulldozer or Zen. Jim Keller often refers to these as "Clean Breaks" that managers typically heavily resist (as real engineering means real tradeoffs and new parts might regress in places). Nevertheless these breaks are essential for significant future improvements.
Of course AMD can continue iterating on Zen, but betting their entire CPU division's future solely on this approach would be strategically unsound.
Speaking of that ...
where are the Zen 7 rumors?
We had information about Zen 4 and Zen 5 circulating 3-4 years before their launch. There is
nothing substantial out there about Zen 7. Perhaps this absence is also telling?