10-09-2017, 09:12 PM
http://techreport.com/blog/32661/just-ho...offee-lake
Quote:This behavior shows why "multi-core enhancement" is undesirable: it's overclocking through and through, and it requires cooling to match. Builders who are buying heatsinks under the assumption they'll be facing all-core Turbo speeds of 4.3 GHz from the i7-8700K could be surprised if their motherboard tries to "help" by modifying Intel's factory Turbo Boost behavior. Our Gigabyte Z370 Aorus Gaming 7 test motherboard commendably ships with the feature disabled, but we'd imagine the feature could still catch both reviewers and builders alike off guard. We've been protesting this "feature" for years, and we'll continue to do so when it rears its head.
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These are all rough benchmarks, but at the end of the day, Coffee Lake does seem to run hotter at stock speeds than the quad-core CPUs that have come before it. That's probably as it should be: there are two more cores and four more threads to deal with under the heat spreader. Builders planning to cool the chip at stock speeds should certainly be able to get away with an inexpensive cooler like a Hyper 212 Evo, but those hoping for a Prime95-stable overclock without a delid and repaste need to budget for a substantial liquid cooler. In that sense, the i7-8700K is no different than the Core i7-6700K and Core i7-7700K before it, and it's definitely harder to cool than AMD's Ryzen CPUs. AMD's chips all boast soldered heat spreaders, and metal is undeniably a better thermal transfer medium than paste.
The question of a paste-based TIM versus solder is almost certainly the largest variable in keeping Coffee Lake on ice relative to Ryzen CPUs, but I think there's more to it than that. First off, it's worth noting that Intel's implementation of AVX in the Skylake microarchitecture offers two 256-bit vector units per core, while the Zen architecture only offers two 128-bit-wide units per core. Skylake also has wider data paths that need more wires to implement, and that presumably means higher power usage when moving data around. When we run an intense AVX workload like Prime95, then, the stress test should unsurprisingly do more work, consume more power, and ultimately generate more heat on a chip that's capable of sustaining twice the SIMD throughput. It's certainly easier to cool an overclocked Ryzen CPU thanks to its soldered heat spreader, but it's hard to argue that one isn't getting more out of overclocking the Core i7-8700K in many tasks despite its higher temperatures. That fact should be part of the value consideration when setting out to overclock either chip.
Whether Intel is doing the best it can to support overclocking on its chips through its thermal interface material of choice is another question, and it's one that's raged since Ivy Bridge and coursed through Devil's Canyon. Coffee Lake doesn't do anything to quench the flames. Folks seeking the lowest load temperatures and highest possible overclocking headroom from Coffee Lake chips will likely need to reach for liquid-metal TIM, their delid tool of choice, and a hefty liquid cooler or giant tower heatsink. At stock speeds, though, the i7-8700K should be fine with the same Cooler Master Hyper 212 Evo that's graced countless systems. Just be sure to terminate any multi-core enhancement settings in your motherboard's firmware with extreme prejudice first.