Intel’s Rocket Lake is expected to deliver a 20 percent IPC improvement, but new rumors suggest the top-end desktop version of the chip will still draw a lot of power at peak loads. The CPU reportedly runs up to 98C with a sustained power consumption of ~ 250W.
According to reports from Chiphell, the Core i9-11900KF was tested with an entry-level 360mm cooler while running AIDA64’s FPU stress test. One reason you should take these rumors with a grain of salt is that AIDA64’s FPU stress test is specifically designed to hammer the chip. This is great if your goal is to test stress test equipment and isolate faults. It’s less great if your goal is to measure normal workload power consumption. AIDA64’s FPU test also includes AVX-512 instructions. If it uses that code path for the Core i9-11900KF while the CPU is clocked at 4.8 GHz, it will generate a lot of heat.
Image by Chiphell
Running the CPU as hot as 98C isn’t ideal from an enthusiast’s perspective, but it can also show that Intel is comfortable running its silicon at this temperature. Years ago, I had a conversation with an Intel engineer, who told me that the company expected its then-current Nehalem and Westmere CPUs to run perfectly at 95 ° C in 24/7 operation, and that the chips are like should be able to handle temperatures for at least a decade. This doesn’t mean enthusiasts should ditch their expensive coolers and bake their chips under a $ 15 heatsink + fan, but the fact that the CPU can run up to 98C isn’t automatically an issue.
It’s not surprising (assuming this rumor is even true) to see the 11900KF running so hot. As we’ve discussed recently, motherboard OEMs often program enthusiastic boards with system standards that will keep the CPU running at full power for a much longer period of time than Intel indicates. Intel is aware of this and its own guidelines are recommendations, not requirements. Normally we would expect a CPU with AVX-512 code to downclock itself. The fact that it hasn’t could mean that Rocket Lake is keeping its clocks in AVX-512 workloads where other Intel CPUs are stepping down. It can also indicate that the motherboard is configured not to drop the multiplier during AVX-512 when running AVX-512 code. Just because this chip hit 98C in an unknown configuration doesn’t mean this will be normal behavior for every CPU.
Intel has chosen to push Rocket Lake as far as possible while remaining backward compatible with Comet Lake, which includes defined TDP ranges. In this way, it’s not much different from AMD’s decision to keep the Ryzen 5000 series maximum TDPs identical to their Ryzen 3000 counterparts. Intel can still claim an increase in energy efficiency as long as it completes workloads in less time than 10th generation chips within the same power range.
Rocket Lake is expected to deliver strong performance improvements in single-threaded workloads and a slightly smaller increase in multi-threaded workloads. Comet Lake finished with 10 cores, while Rocket Lake offers only eight, but the IPC gains are expected to largely or completely offset them. In fact, AVX-512 support can give the 8-core Core i9-11900K a few wins over the 10-core Comet Lake, although this depends on benchmark support.
We’ll know more when Rocket Lake launches in late March.
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