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: DDR5 vs DDR4
Traditionally we test our memory settings at JEDEC specifications. JEDEC is the standards body that determines the requirements for each memory standard. In this case, the Core i9 supports the following aligning with those standards:
- DDR4-3200 CL22
- DDR5-4800B CL40*
There's an * next to the DDR5 for a couple of reasons. First, when asked, Intel stated that 4800A (CL34) was the official support, however since the technical documents have now been released, we've discovered that it is 4800B (CL40). Secondly, 4800B CL40 technically only applies to 1 module per 64-bit channel on the motherboard, and only when the motherboard has two 64-bit slots to begin with. We covered Intel's memory support variants in a previous article, and in this instance, we're using DDR5-4800B memory in our testing.
As explained in our SPEC section, DDR5 memory not only brings bandwidth improvements but also the increased number of channels (4x32-bit vs 2x64-bit) means that the memory can be better utilized as threads pile on the memory requests. So while we don't see much improvement in single threaded workloads, there are a number of multi-threaded workloads that would love the increased performance.
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michael2k - Thursday, November 4, 2021 - link
One is a bellwether for the other.Mobile parts will have cores and clocks slashed to hit mobile power levels; 7W-45W with 2p2e - 6p8e
However, given that a single P core in the desktop variant can burn 78W in POV Ray, and they want 6 of them in a mobile part under 45W, that means a lot of restrictions apply.
Even 8 E cores, per this review, clock in at 48W!
That suggests a 6p8e part can't be anywhere near the desktop part's 5.2GHz/3.9GHz Turbo clocks. If there is a linear power-clock relationship (no change in voltage) then 8 E cores at 3GHz will be the norm. 6 P cores on POV-Ray burn 197W, then to hit 45W would mean throttling all 6 cores to 1.2GHz
https://hothardware.com/news/intel-alder-lake-p-mo...
siuol11 - Thursday, November 4, 2021 - link
Except that we know that the power-clock ratio is not linear and never has been. You can drop a few hundred MHz off of any Intel chip for the past 5 generations and get a much better performance per watt ratio. This is why mobile chips don't lose a lot of MHz compared to desktop chips.michael2k - Thursday, November 4, 2021 - link
We already know their existing Ice Lake 10nm 4C mobile parts are capped at 1.2GHz to hit 10W:https://www.anandtech.com/show/15657/intels-new-si...
A 6p8e part might not clock that low, but I'm certain that they will have to for the theoretical 7W parts.
Here's a better 10nm data point showing off their 15W-28W designs:
https://www.anandtech.com/show/14664/testing-intel...
4C 2.3GHz 28W TDP
Suggests that a 4pNe part might be similar while the 6p8e part would probably be a 2.3GHz part that could turbo up to a single core to 4GHz or all cores to 3.6GHz
TheinsanegamerN - Thursday, November 4, 2021 - link
Yes, once it gets in the way of performance, and intel's horrible efficiency means you need high end water cooling to keep it running, whereas AMD does not. Intel's inneficiency is going to be an issue for those who like air cooling, which is a lot of the market.Wrs - Thursday, November 4, 2021 - link
Trouble is I'm not seeing "horrible efficiency" in these benchmarks. The 12900k is merely pushed far up the curve in some of these benches - if the Zen3 parts could be pushed that far up, efficiency would likewise drop quite a bit faster than performance goes up. Some people already do that. PBO on the 5900x does up to about 220W (varies on the cooler).jerrylzy - Friday, November 5, 2021 - link
PBO is garbage. You can restrict EDC to 140A, let loose other restrictions and achieve a better performance than setting EDC to 220A.Spunjji - Friday, November 5, 2021 - link
"if the Zen3 parts could be pushed that far up"But you wouldn't, because you'd get barely any more performance for increased power draw. This is a decision Intel made for the default shipping configuration and it needs to be acknowledged as such.
Wrs - Saturday, November 6, 2021 - link
As a typical purchaser of K chips the default shipping configuration holds rather little weight. A single BIOS switch (PBO on AMD, MTP on Intel), or one slight change to Windows power settings, is pretty much all the efficiency difference between 5950x and 12900k. It pains me every time I see a reviewer or reader fail to realize that. The chips trade blows on the various benches because they're so similar in efficiency, yet each by their design has strong advantages in certain commonplace scenarios.Spunjji - Friday, November 5, 2021 - link
If the competition are able to offer similar performance and you don't have to shell out the cash and space for a 360mm AIO to get it, that's a relevant advantage. If those things don't bother you then it's fine, though - but we're in a situation where AMD's best is much more power efficient than Intel's at full load, albeit Intel appears to reverse that at lower loads.geoxile - Thursday, November 4, 2021 - link
Clock/power scales geometrically. The 5900HS retains ~85% of the 5800X's performance while using 35-40W stable power vs 110-120W for the 5800X. That's almost 3x more efficient. Intel is clocking desktop ADL to the moon, it doesn't mean ADL is going to scale down poorly, if anything I expect it to scale down very well since the E-cores are very performant while using a fraction of the power and according to Intel can operate at lower voltages than the P-cores can, so they can scale down even lower than big cores like ADL P-cores and zen 3. ADL mobile should be way more interesting than ADL desktop.