Comment by jfindley | Hacker News Reader

Comment by jfindley | Hacker News Reader

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Do note though that AIUI these are all E-cores, have poor single-threaded performance and won't support things like AVX512. That is going to skew your performance testing a lot. Some workloads will be fine, but for many users that are actually USING the hardware they buy this is likely to be a problem.

If that's you then the GraniteRapids AP platform that launched previously to this can hit similar numbers of threads (256 for the 6980P). There are a couple of caveats to this though - firstly that there are "only" 128 physical cores and if you're using VMs you probably don't want to share a physical core across VMs, secondly that it has a 500W TDP and retails north of $17000, if you can even find one for sale.

Overall once you're really comparing like to like, especially when you start trying to have 100+GbE networking and so on, it gets a lot harder to beat cloud providers - yes they have a nice fat markup but they're also paying a lot less for the hardware than you will be.

Most of the time when I see takes like this it's because the org has all these fast, modern CPUs for applications that get barely any real load, and the machines are mostly sitting idle on networks that can never handle 1/100th of the traffic the machine is capable of delivering. Solving that is largely a non-technical problem not a "cloud is bad" problem.

These Intel Darkmont cores are in a different performance class than the (Crestmont) E-cores used in the previous generation of Sierra Forest Xeon CPUs. For certain workloads they may have even a close to double performance per core.

Darkmont is a slightly improved variant of the Skymont cores used in Arrow Lake/Lunar Lake and it has a performance very similar to the Arm Neoverse V3 cores used in Graviton5, the latest generation of custom AWS CPUs.

However, a Clearwater Forest Xeon CPU has much more cores per socket than Graviton5 and it also supports dual-socket motherboards.

Darkmont also has a greater performance than the older big Intel cores, like all Skylake derivatives, inclusive for AVX-using programs, so it is no longer comparable with the Atom series of cores from which it has evolved.

Darkmont is not competitive in absolute performance with AMD Zen 5, but for the programs that do not use AVX-512 it has better performance per watt.

However, since AMD has started to offer AVX-512 for the masses, the number of programs that have been updated to be able to benefit from AVX-512 is increasing steadily, and among them are also applications where it was not obvious that using array operations may enhance performance.

Because of this pressure from AMD, it seems that this Clearwater Forest Xeon is the final product from Intel that does not support AVX-512. Both next 2 Intel CPUs support AVX-512, i.e. the Diamond Rapids Xeon, which might be launched before the end of the year, and the desktop and laptop CPU Nova Lake, whose launch has been delayed to next year (together with the desktop Zen 6, presumably due to the shortage of memories and production allocations at TSMC).

E-cores aren't that slow, yesteryear ones were already around Skylake levels of performance (clock for clock). Now one might say that's a 10+ year old uarch, true, but those ten years were the slowest ten years in computing since the beginning of computing, at least as far as sequential programs are concerned.

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