I was kind of hoping we wouldn't see one of these until the end of the year or so, but what's the fun in that?
The usual questions spring to mind:
- Will it support currently existing motherboards (300/400/500 series chipsets)?
- What kind of IPC increase are we talking about?
- Will AMD manage to squeeze more frequencies?
- What node will it use?
- What will be its TDP?
- Will it support AVX512 instructions?
- When and if we can expect Ryzen 4000 CPUs with modern onboard graphics (e.g. Navi10/Navi20)?
1] At least 400 up, which would also mean 300 unless there was unnecessary segmentation
2] Less than Zen 2. They got the low hanging fruit I think. 10%
3] I think we'll see higher frequencies before Zen 3. There was a rumored 5GHz Zen 2 early next year. If that happens, no. If current frequencies stand, yes. Around 4.9-5.0Ghz.
4] 7nm+ (though I wouldn't be surprised to see 6nm, which would probably be the "safe" choice)
5] Similar. We may see something new like 45W parts though.
6] Hard no
7] Surprisingly (IMO) APU's haven't been a big priority. Since I think Zen 3 will be late Q3/early Q4 2020, I'll say Q2 2021 at the earliest.
As far as IPC is concerned, Zen 3 will have to bring a 15%+ uplift in order to match Sunny Cove. I don't believe in the rumors that there will be 4-way SMT, as that is just wasteful for consumer workloads. Besides the SMT yield is even higher on Zen 2 compared to Zen/Zen+, which means that the front-end is still a bottleneck in the design, despite the new branch predictor and increased uop-cache.
I would also like AMD to move away from the CCX-design, as it makes no sense now that they've committed to the chiplet approach. This will allow them to unify L3 among all cores, leading to a better cache policy and lesser reliance on IF links for inter-core communication. This would probably mean a ring-bus configuration, which will impact core-to-core latency between nearest cores but should give better overall latency between near and far cores.
I disagree about the 15% IPC. I don't think they will reach it. Also, look at Icelake on mobile. It shows solid IPC gains but it loses so much frequency it basically evens out. I expect the same on desktop, if we even see 10nm on desktop. It looks more likely Intel is going straight to 7nm there as they know 10nm wouldn't give them anything on top of 14nm+++ since it clocks so high.
I agree, there will be no SMT4. Don't know where that rumor came from. Probably the same AMD fans that predicted 5GHz+ Zen 2 blowing away Intel is bargain basement prices. That stuff gets old.
I think AMD is too invested in the CCX design to scrap it and I don't think they could in a year's time anyway. I expect the cache to be much of the same this time around. Maybe they'll shrink the I/O die and through some on there though? I would love a true LLC but I'm not sure how they get there just yet.
I think Zen 3 goes wider. Right now it can do what, decode 4 as well as dispatch 2 ups for a total of 6? I could see them adding a decoder. Beyond that I'd have to look at the slides to see where some of the bottlenecks might be.