Friday, 16 July 2021

Alder Lake Leak: Intel Core i9-12900K Offers 5.3GHz Boost Clock, Lower PL2

Specifications for Intel’s upcoming Alder Lake have leaked, and they imply a CPU that’s at least somewhat more power-efficient than its predecessors without giving up any top-end clock. As always, all leaks should be taken as rumors, not facts.

These leaks, from the Chinese forum Zhihu, suggest the Core i9-12900K will match the 5.3GHz top clock on the Core i9-11900K, with an all-core boost frequency of 5GHz. The CPU’s PL1 is 125W and its PL2 is 228W. The PL1 value is in line with other Intel processors currently in-market, while the PL2 of 228W is down somewhat from the 250W of current Intel chips. This could indicate that Intel has improved top-line power consumption under load compared with its 14nm CPUs, though it’s also possible that Intel tightened the specification for other purposes.


One interesting facet of Intel’s approach to hybrid cores as opposed to what Apple has shown is that Intel appears to be targeting much higher clock speeds for its “little” cores. The 10nm(++) Gracemont cores will top out between 3.4GHz and 3.9GHz. The fact that they clock 15 percent higher on the top-end Intel part could be a clue about where the company expects performance differentiation to show up in its product stack. Pushing up the clock on Gracemont gives Intel a little more headroom on those cores before moving workloads over to Golden Cove.

Apple’s M1 tops out at just 2GHz for its high-efficiency cores. The all-core boost on Golden Cove is 1.28x higher than Gracemont, which means the performance kick from moving a workload to the “big” cores should still be substantial. Golden Cove is expected to be ~1.2x higher IPC than Intel’s previous big-core CPUs, while Gracemont is reportedly targeting Skylake IPC. Actually hitting Skylake IPC would make the performance gap between Gracemont and Golden Cove pretty small. Plenty of people are still using Skylake or earlier CPUs in everyday systems, and Intel’s Kaby Lake, Coffee Lake, and similar CPUs are all effectively Skylake as well, architecturally speaking.

It’s always risky to guess the performance a CPU will offer before launch. Reports have suggested Alder Lake could offer competitive performance with AMD’s Ryzen 5950X. I’m not going to say this cannot happen, but it would require a few things to be true. First, Intel would need to absolutely nail both its IPC improvements and its clock speeds. Alder Lake can’t afford to give back any frequency at all to hit this kind of uplift. Second, it would have to deliver on the idea of Gracemont as a Skylake competitor. Third, it would need to be able to engage both its big and its little cores simultaneously while remaining within its power envelope.

We have seen both Intel and AMD deliver 30-50 percent performance improvements in a single generation before, so I’m not going to call the idea preposterous, but Alder Lake will need to be an exceptional CPU to offer competition against the 16-core Ryzen 5950X. While the two chips are both technically 16-core, Alder Lake’s hybrid model would typically be expected to offer better power efficiency and possibly better responsiveness, but not match AMD in top-end raw performance. Gracemont does not support Hyper-Threading, so its ability to provide an additional kick is likely a bit more limited than what we’d expect from another eight “big” cores.

Alder Lake is expected to debut in late 2021 or early 2022, depending on Intel’s launch schedule. Zen 3 CPUs with large additional pools of L3 cache may arrive in market at roughly the same time. It’s been implied that the additional L3 could offer a ~1.15x performance boost for Zen 3, allowing AMD to deliver roughly one generation’s worth of improvement at the same clock, or potentially offering more power-efficient chips with equivalent performance to the previous generation at lower clocks.

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