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Sky Lake Refresh Refresh Refresh Refresh comes to desktops
Way back on August 5, 2015, Intel launched Sky Lake. Their flagship CPU was the Core i7-6700K, which had four cores with a max turbo of 4.2 GHz. With AMD mired in Bulldozer derivatives that required too much power for too little performance, it was easily the best mainstream consumer CPU on the market. It had an MSRP of $339, and no included heatsink, but with a TDP of 91 W, cooling it was easy enough.
Step forward a little less than five years and Intel has now launched the Core i9-10900K, as well as some lower end versions of the same thing. It is the same CPU core architecture on the same process node as the original Sky Lake. Well, kind of. Intel is calling it 14++ nm rather than 14 nm, but it's really just a more mature, better optimized version of the 14 nm node. There wasn't supposed to be a Sky Lake Refresh at all, let alone four refreshes. It was supposed to be on to Cannon Lake on 10 nm, except that the process node didn't work.
Without the ability to move to a new process node, which is traditionally what has driven long-term performance improvements, Intel had to instead add cores and frequency in order to improve performance. What happens to power if you go from a 4-core CPU with a max turbo of 4.2 GHz to a 10-core CPU with a max turbo of 5.3 GHz? If you think power consumption only increases from 91 W to 125 W, then you must work for Intel marketing. The nominal TDP is 125 W, but that's basically meaningless for this CPU.
The PL2 is 250 W, meaning that when turbo is engaged, the CPU could use up to 250 W. Motherboard manufacturers customarily ignore Intel's nominal recommendations and allow turbo to be on all the time, or perhaps rather, except when idle. If they don't, then their competitors will, and their motherboard will look like it makes the CPU perform much worse. So really, this is a 250 W CPU.
That leads to the question, how do you cool a 250 W CPU? There are basically three options: an enormous air cooler, a liquid cooling system with a huge radiator, or something more exotic like a water chiller or phase change cooling. It's a similar problem to trying to cool a 280 W AMD Threadripper CPU, though Threadripper's several dies spread out the heat a lot more to begin with. Oh, and that Threadripper CPU has vastly more cores, and offers much higher performance in well-threaded applications to justify that high power consumption.
AnandTech measured the CPU as using up to 254 W when pushing all cores hard. For comparison, the Ryzen 9 3950X topped out just under 145 W in the same test. And the Ryzen CPU has 16 cores rather than 10 and generally crushes the Core i9-10900K at anything that can use all those cores, even while using far less power. For another comparison, the Ryzen Threadripper 3990X weighs in at 280 W, and it has 64 cores. Once you factor in the need for an extravagant cooling system, the Core i9-10900K is going to be far more expensive than the 12-core Ryzen 9 3900X, though likely still cheaper than the 3950X.
So why would anyone want a CPU that burns so much power without offering a ton of cores? Because that's the way to get the highest possible single-threaded CPU performance, of course. The extent to which single-threaded performance matters to gaming is often exaggerated, as a hypothetical single-core Sky Lake CPU that clocked at 6 GHz would actually be pretty terrible. But 10 cores is still a lot, and in the useful lifetime of the CPU, it's going to be rare for any game to offer any meaningful benefit to 16 cores over "only" 10. Intel rightly claims that the Core i9-10900K offers the highest single-threaded CPU performance you can buy, and commonly the highest gaming performance, at least if the CPU is the bottleneck.
Of course, another way to offer higher clock speeds is to really push the physical limits of what the CPU can handle. For the Core i9-10900K, Intel lists 5 different turbo speeds. Basically, they promise that any core can clock up to 5.1 GHz, at least two particular cores can hit 5.2 GHz, all the cores can clock up to 4.8 GHz at once, and you can add 100 MHz to any of those numbers if the CPU is under 70 C. Good luck keeping a CPU under 70 C while it is using 250 W, though that could be far more realistic if you're only using one or two cores.
The stock clocks on the Core i9-10900K are high enough that you're not really going to be able to overclock it yourself apart from exotic cooling. For comparison, the Core i7-6700K had a nominal max turbo of 4.2 GHz, but you could probably overclock it to about 4.5 GHz if you wanted to. Now, having a CPU stock clocked more aggressively and able to adjust things at a much finer granularity than is possible with a manual overclock is a good thing. But still, 250 W. Of course, if 250 W bothers you, then you can just dismiss Intel out of hand and have a look at AMD's lineup.
The Core i7-10700K is basically a Core i9-9900K, except that Intel now promises that some two of the physical cores (but not necessarily the ones you're using) can clock 100 MHz higher than before. The Core i5-10600K is basically a Core i7-9700K but with the turbo dropped by 100 MHz. But that isn't a necessarily a bad thing, as dropping those CPUs by a tier in Intel's lineup means corresponding price drops. Which, of course, Intel basically had to do in order to be at all competitive with AMD.
The upshot is that Intel retains the single-threaded CPU performance crown for another day, though it comes at the expense of fairly ridiculous power consumption. But even that performance crown might not last the rest of the year. AMD has promised that Zen 3 will launch this year.
Step forward a little less than five years and Intel has now launched the Core i9-10900K, as well as some lower end versions of the same thing. It is the same CPU core architecture on the same process node as the original Sky Lake. Well, kind of. Intel is calling it 14++ nm rather than 14 nm, but it's really just a more mature, better optimized version of the 14 nm node. There wasn't supposed to be a Sky Lake Refresh at all, let alone four refreshes. It was supposed to be on to Cannon Lake on 10 nm, except that the process node didn't work.
Without the ability to move to a new process node, which is traditionally what has driven long-term performance improvements, Intel had to instead add cores and frequency in order to improve performance. What happens to power if you go from a 4-core CPU with a max turbo of 4.2 GHz to a 10-core CPU with a max turbo of 5.3 GHz? If you think power consumption only increases from 91 W to 125 W, then you must work for Intel marketing. The nominal TDP is 125 W, but that's basically meaningless for this CPU.
The PL2 is 250 W, meaning that when turbo is engaged, the CPU could use up to 250 W. Motherboard manufacturers customarily ignore Intel's nominal recommendations and allow turbo to be on all the time, or perhaps rather, except when idle. If they don't, then their competitors will, and their motherboard will look like it makes the CPU perform much worse. So really, this is a 250 W CPU.
That leads to the question, how do you cool a 250 W CPU? There are basically three options: an enormous air cooler, a liquid cooling system with a huge radiator, or something more exotic like a water chiller or phase change cooling. It's a similar problem to trying to cool a 280 W AMD Threadripper CPU, though Threadripper's several dies spread out the heat a lot more to begin with. Oh, and that Threadripper CPU has vastly more cores, and offers much higher performance in well-threaded applications to justify that high power consumption.
AnandTech measured the CPU as using up to 254 W when pushing all cores hard. For comparison, the Ryzen 9 3950X topped out just under 145 W in the same test. And the Ryzen CPU has 16 cores rather than 10 and generally crushes the Core i9-10900K at anything that can use all those cores, even while using far less power. For another comparison, the Ryzen Threadripper 3990X weighs in at 280 W, and it has 64 cores. Once you factor in the need for an extravagant cooling system, the Core i9-10900K is going to be far more expensive than the 12-core Ryzen 9 3900X, though likely still cheaper than the 3950X.
So why would anyone want a CPU that burns so much power without offering a ton of cores? Because that's the way to get the highest possible single-threaded CPU performance, of course. The extent to which single-threaded performance matters to gaming is often exaggerated, as a hypothetical single-core Sky Lake CPU that clocked at 6 GHz would actually be pretty terrible. But 10 cores is still a lot, and in the useful lifetime of the CPU, it's going to be rare for any game to offer any meaningful benefit to 16 cores over "only" 10. Intel rightly claims that the Core i9-10900K offers the highest single-threaded CPU performance you can buy, and commonly the highest gaming performance, at least if the CPU is the bottleneck.
Of course, another way to offer higher clock speeds is to really push the physical limits of what the CPU can handle. For the Core i9-10900K, Intel lists 5 different turbo speeds. Basically, they promise that any core can clock up to 5.1 GHz, at least two particular cores can hit 5.2 GHz, all the cores can clock up to 4.8 GHz at once, and you can add 100 MHz to any of those numbers if the CPU is under 70 C. Good luck keeping a CPU under 70 C while it is using 250 W, though that could be far more realistic if you're only using one or two cores.
The stock clocks on the Core i9-10900K are high enough that you're not really going to be able to overclock it yourself apart from exotic cooling. For comparison, the Core i7-6700K had a nominal max turbo of 4.2 GHz, but you could probably overclock it to about 4.5 GHz if you wanted to. Now, having a CPU stock clocked more aggressively and able to adjust things at a much finer granularity than is possible with a manual overclock is a good thing. But still, 250 W. Of course, if 250 W bothers you, then you can just dismiss Intel out of hand and have a look at AMD's lineup.
The Core i7-10700K is basically a Core i9-9900K, except that Intel now promises that some two of the physical cores (but not necessarily the ones you're using) can clock 100 MHz higher than before. The Core i5-10600K is basically a Core i7-9700K but with the turbo dropped by 100 MHz. But that isn't a necessarily a bad thing, as dropping those CPUs by a tier in Intel's lineup means corresponding price drops. Which, of course, Intel basically had to do in order to be at all competitive with AMD.
The upshot is that Intel retains the single-threaded CPU performance crown for another day, though it comes at the expense of fairly ridiculous power consumption. But even that performance crown might not last the rest of the year. AMD has promised that Zen 3 will launch this year.
