The Intel 12th Gen Core i9-12900K Review: Hybrid Performance Brings Hybrid Complexity
by Dr. Ian Cutress & Andrei Frumusanu on November 4, 2021 9:00 AM ESTCPU Benchmark Performance: E-Core
In this batch of testing, we're focusing primarily on the E-cores. Intel claimed that the performance was around the level of its Skylake generation of processors (6th Gen to 10th Gen, depending which slide you read), and we had to put that to the test. In this instance, we're comparing to the flagship Skylake processor, the Core i7-6700K, which offered 4C/8T at 91 W. We also did a number of multi-threaded tests to see where the E-cores would line up.
In order to enable E-core only operation, we used affinity masks.
Single Threaded
In these few tests, we can see that the E-core is almost there at 4.2 GHz Skylake. Moving down to 3.9 GHz, perhaps something like the i7-6700, would put it on par.
Multi-Thread Tests
Having a full eight E-cores compared to Skylake's 4C/8T arrangement helps in a lot of scenarios that are compute limited. When we move to more memory limited environments, or with cross-talk, then the E-cores are a bit more limited due to the cache structure and the long core-to-core latencies. Even with DDR5 in tow, the E-cores can be marginal to the Skylake, for example in WinRAR which tends to benefit from cache and memory bandwidth.
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mode_13h - Sunday, November 7, 2021 - link
I'm not even going to say this is a bad idea. The problem is that it's a big change and Intel normally prepares the software developer community for big new ISA extensions a year+ in advance!Again, what you're talking about is an ABI change, which is a big deal. Not only that, but to require code to handle dynamically switching between AVX2 and AVX-512 paths means that it can't use different datastructures for each codepath. It even breaks the task pre-emption model, since there need to be some limitations on where the code needs to have all its 512-bit registers flushed so it can handle switching to the AVX2 codepath (or vice versa).
This adds a lot of complexity to the software, and places a greater testing burden on software developers. All for (so far) one CPU. It just seems a bit much, and I'm sure a lot of software companies would just decide not to touch AVX-512 until things settle down.
GeoffreyA - Sunday, November 7, 2021 - link
My view on this topic is that Intel made a sound decision disabling AVX512. Some of the comments are framing it as if they made a mistake, because the tech community discovered it was still there, but I don't see any problem. Only, the wording was at fault, this controversial "fused off" statement. And actually, the board makers are at fault, too, enabling a hidden feature and causing more confusion.On the question of whether it's desirable, allowing one core with the instructions and another without, would've been a recipe for disaster---and that, too, for heaven knows what gain. The simplest approach was bringing both cores onto the same footing. Indeed, I think this whole P/E paradigm is worthless, adding complexity for minimal gain.
Oxford Guy - Monday, November 8, 2021 - link
‘Intel made a sound decision disabling AVX512’That’s not what happened.
O-o-o-O - Sunday, November 7, 2021 - link
Really? Our tech guys tried out Xeon Phi but couldn't make use of it. Years later, Xeon Phi was abruptly discontinued due to lack of demand. GPGPUs are much easier to handle.Yeah, coding cost and risks aside, it's interesting to see complex work of art in the modern CPU. But I'd rather wish for expansion of GPU support (like shared memory and higher band-width).
kwohlt - Sunday, November 7, 2021 - link
My understanding is that Raptor Lake's change is replacing Golden Cover P cores with Raptor Cove P cores, doubling Gracemont E-Cores per SKU, and using the same Intel 7 process. Granted, it's all leaks at this point, but with Gracemont being reused for Raptor Lake, I don't expect AVX-512 next year either.mode_13h - Monday, November 8, 2021 - link
> Raptor Lake's change is ... doubling Gracemont E-Cores ... using the same Intel 7 process.I was merely speculating that this *might* just be a transient problem. If they're using the same process node for Raptor Lake, which seems very plausible, then it's understandable if they don't want to increase the size or complexity of their E-cores.
However, there's some precedent, in the form of Knights Landing, where Intel bolted on dual AVX-512 pipelines + SMT4 to a Silvermont Atom core. And with a more mature Intel 7 node, perhaps the yield will support the additional area needed for just a single pipe + 512-bit registers. And let's not forget how Intel increased the width of Goldmont, yet simply referred to it as Goldmont+.
So, maybe Raptor Lake will use Gracemont+ cores that are augmented with AVX-512. We can hope.
GURU7OF9 - Saturday, November 6, 2021 - link
The is by far the best review I have read so far.A great comparison I would love to see just out of curiouslty would be to see P core only benchmarks and then e core only benchmarks! We could gain a much better understanding of the capabilities and performance of both .
This would bring a little bit of familiarity back to benchmarking .
nunya112 - Saturday, November 6, 2021 - link
the only info provided was its on intels new process 7 node. what does that mean? are they using TSMC and at 7nm? or did they finally crack 7nm at Intel?mode_13h - Sunday, November 7, 2021 - link
"Intel 7" is the process node formerly known as "10 nm ESF" (Enhanced SuperFin), which is the 4th generation 10 nm process, counting by the revisions they've introduced between the different products based on it. They like to pretend that Cannon Lake didn't happen, but that's why Ice Lake was actually 10 nm+ (2nd gen).They rebranded 10 nm ESF as "Intel 7" for marketing reasons, as explained here:
https://www.anandtech.com/show/16823/intel-acceler...
Hossein - Sunday, November 7, 2021 - link
It's funny that most reviewers are conveniently silent about the fact that there are quite a 'few' games which are incompatible AL.