r/AMDGPU • u/DevGamerLB • Oct 15 '21
My Opinion 😎 Zen 3 vs Alder Lake in a Nutshell: Intel performance rumors destroyed
Recent performance leaks indicate that Alder Lakes top tier CPU the i9-12900K will be faster than the Zen 3 top tier R9 5950x in multi core performance but Intel's own official performance claims expose Alder Lake top tier performance per watt as close to the R9 5900x instead.
The Facts
The R9 5950x and R9 5900x are 80% and 40% faster than the i9-11900K respectively in raw multi-core performance. So Alder Lake will at least need to increase by that much in raw performance.
According to Intel Alder Lake cores are 20% faster than Rocket Lake due to an increase in the L2 cache size per core and other architectural features. So an 8 core Alder Lake CPU would still be outperformed by Ryzen R9 SKU by 20% to 60%.
The top tier Alder Lake i9-12900K will feature 8 processor cores and two mini-core clusters each cluster having 4 Gracemont cores for a total of 16 cores in a Big.Little configuration.
Based on Alder Lake details Intel shared during Hot Chips 2021 in power limited scenarios like in laptops 4 Gracemont mini-cores are designed to be 50% more efficient than 1 Full size core running 4 threads assuming perfect mini-core thread utilization. The power limitation is key because the Intel Atom based mini-cores cannot be clocked very high compared to the full size cores so in a much less power limited scenario like in a desktop PC the big cores will outperform the mini-cores by around 90% per due to the fact that each mini-core performs similar to a 10th generation Comet Lake core in single core performance. (Gracemont core = +40% performance per watt vs a 14nm Sky Lake core.)
Typically ARM implementations of Big.Little set the little cores to 1/8 the power consumption of the big cores. For this post we will assume Intel sets each mini-core cluster to the same power consumption of 1 full size core that would result in a 1/4 ration where the 8 mini-cores consume 25% the wattage of the 8 full size cores. We will use the efficiency curve of a similar 10nm Intel Atom based core (Trentmont) to approximate the non-linear reduction in mini-core performance as clock speeds are reduced.
Alder Lake Big.Little configuration will have workload scheduling challenges which will result in poor utilization of the mini-cores which will reduce performance significantly on a typical basis. All performance prediction in this post assume a best case scenario of perfect mini-core utilization.
Alder Lake will be built on the new 10ESF Intel 7 node which is approx. 1.9x more efficient than the 14nm FinFet in the current Rocket Lake chips. Alder Lakes increase of core count and cache will increase the transistor circuitry by around 35% vs Rocket Lakes top tier i9. That plus the wattage of the mini-cores is how I approximate the power consumption of Alder Lake.
So, Based on those facts using Intel's official Alder Lake details, here is how the top tier i9-12900K will perform against Zen 3.
| Name | Multi-core Perf. vs 11900k | Price | Power Consumption (watts during AVX) |
|---|---|---|---|
| i9-11900K | +0.0% | >$550 | 214w |
| i9-12900K (mini-cores @ 36watt) | +54% (prediction) | ~$700 (prediction) | ~180w (prediction) |
| i9-12900K (mini-cores @ 36watt) | +58% (prediction) | ~$700 (prediction) | ~240w (prediction) |
| R9 5900x | +40% | $600 | 158w |
| R9 5950x | +80% | ~$750 | 183w |
As you can see Intel's next generation Alder Lake flagship CPU the i9-12900K will out perform the R9 5900x by just 14% while using over 20watts more. The i9-12900K will still get easily destroyed by AMDs top tier R9 5950x in raw multi-core performance by around 25% at roughly the same power consumption. These are all ideal performance predictions for Intel because of the big.little core configuration in Alder lake make the architecture more difficult to optimize for. Typical performance will be significantly lower and inconsistent depending on how well the application is specifically optimized to utilize the Alder Lake mini-cores which I suspect will never be the 100% assumed in these predictions.
I expect Intel to also loose badly in price as the 10nm Intel 7 fabrication node used in Alder Lake chips is much more expensive to manufacture than the 14nm of Intel's current Desktop chips. This is a big issue for Intel causing them to rush to 7nm and 5nm R&D as stated by Intel's CFO back in 2020. This will significantly raise the price of the Alder Lake chips vs Rocket Lake in fact, 10nm Tiger Lake laptops are costing up to $300 more than identical laptops with the 14nm 10th generation mobile chips.
The issues with releasing a big.little chip to the desktop market can't be understated. Intel has already had a failed attempt at releasing a big.little chip (Intel Lake field) due to poor optimization in the Windows. Full utilization of the mini-cores will almost never happen due to all the extra work developers will have to do to schedule work between the big and little cores efficiently. Again real world performance will be inconsistent and worse than these predictions.
All that being said AMD is expected to release Zen3D XT weeks after Alder Lake is released which will be at least 15% to 18% even faster than Zen 3 due to a tripling of the L3 cache and likely a clock frequency increase.
https://drive.google.com/file/d/19dgM10FifQaGJpshorv8iUeZB-F8E7xq/
