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Sizing up the lineup

Model Base clock Single-core
Turbo Boost 2.0
frequency
Cores/
threads
TDP L2
cache
L3
cache
Memory
speed (MT/s)
Price
Core i7-8700K 3.7 GHz 4.7 GHz 6/12 95W 1.573
MB
12MB Dual DDR4-2666 $359
Core i7-8700 3.2 GHz 4.6 GHz 65W $303
Core i5-8600K 3.6 GHz 4.3 GHz 6/6 95W 9MB $257
Core i5-8400 2.8 GHz 4 GHz 65W $182
Core i3-8350K 4 GHz N/A 4/4 91W 1.05
MB
6MB Dual DDR4-2400 $168
Core i3-8100 3.6 GHz 65W $117

As it's implemented in the six chips launching today, Coffee Lake really is just a six-core Skylake die at an architectural level. The increase to 12MB of L3 cache on Coffee Lake Core i7s is the natural consequence of adding two more cores with 2MB of L3 each. Coffee Lake Core i5s and Core i3s get 1.5 MB of L3 per core to play with. Outside of those broad changes, Coffee Lake is, as we've noted, largely a product of process refinement and small tweaks, like the boost to natively-supported DDR4-2666 RAM on some parts.


A block diagram of the Skylake client core. Source: Intel

This is by no means a bad thing. Despite launching in 2015, Skylake is still a world-class architecture, and Intel probably wants to get as much out of it as it can before firing another valuable microarchitecture or process-shrink arrow from its quiver. Doesn't help that the company seems to be struggling with its 10-nm process, either, but that's another topic for another time.

Although price points largely haven't changed in the move to Coffee Lake, buyers are getting more for their money at each rung on Intel's product ladder than ever before. Core i3s now offer four full cores to toy with, and the Core i3-8350K is basically a Core i5-7600K for almost $100 less. That's quite the rough break for AMD's four-core, eight-thread Ryzen 5s and four-core, four-thread Ryzen 3s, as the i5-7600K had enough oomph to match the $190 Ryzen 5 1500X in our productivity tasks while beating it handily in our gaming benchmarks. That's before we consider the i5-7600K's overclocking prowess, as well.

Model Cores Threads Base clock Boost clock Max XFR
headroom
L3 cache TDP Price
Ryzen 5 1600X 6 12 3.6 GHz 4.0 GHz 100 MHz 16MB 95W $249
Ryzen 5 1600 3.2 GHz 3.6 GHz 50 MHz 65W $219
Ryzen 5 1500X 4 8 3.5 GHz 3.7 GHz 200 MHz $189
Ryzen 5 1400 3.2 GHz 3.4 GHz 50 MHz 8MB $169

Up the stack, things look slightly better for the red team. The six-core, six-thread i5-8400 has a Turbo clock of 4 GHz and a base clock of 2.8 GHz in a 65W power envelope. It goes for $20 less than the Ryzen 5 1600, an unlocked, six-core, 12-thread chip for $215 at retail. AMD's effort has a much larger L3 cache, twice the L2 per core, and six threads on the i5-8400. Its stock cooler will likely be much nicer than Intel's boxed heatsink, too, a nice perk for budget builders. I'd expect the i5-8400 to have better performance in lightly-threaded workloads, but the Ryzen 5 1600 could pull ahead in multithreaded tasks, and it could stretch any lead it has even further with some overclocking.

The real part of interest to many enthusiasts may be the $257 Core i5-8600K, whose price naturally pits it against AMD's hottest six-core part, the Ryzen 5 1600X. With six unlocked cores and the considerable overclocking potential of Intel's 14-nm process to play with, the i5-8600K seems an easy list-topper for any midrange system. Even before we look at overclocking, though, the i5-8600K is besting the Ryzen 5 1600X's Turbo speeds with XFR in the picture. The 1600X's SMT support might give it a slight edge in some heavily-threaded workloads at stock speeds, but I imagine overclocking the i5-8600K could easily bridge that gap.


The Core i5-8400

We do have a Core i5-8400 in our labs that arrived alongside the i7-8700K, but in the interest of time, I chose to focus my efforts on the high-end chip first. Intel hasn't sent us an i5-8600K to play with so far, so we may have to source one of our own to see how it handles as part of our i5-8400 review. Neither the i5-8600K nor the 1600X come with a cooler, so buyers are essentially being asked to pick their poison with regard to overclocking or not. As we'll soon see, Coffee Lake's overclocking potential could easily tip the scales in Intel's favor, but I still expect this battle to be a close one, dollar for dollar.

Coffee Lake Core i7s are the most interesting of this bunch, because they mark the first time so many cores and threads have ever been available on Intel's mainstream desktop platform. In fact, these chips have specifications that used to be reserved for the blue team's high-end desktop CPUs, and I have every reason to expect their performance will belong in that tier.

For $303, the i7-8700's base clock matches the Turbo Boost speed of the Broadwell-E Core i7-6800K, and its Turbo speeds go all the way up to a very impressive 4.6 GHz. No, you're not getting unlocked multipliers, quad-channel memory, or a ton of PCIe lanes to play with from the i7-8700, but I still think many builders will be elated with this kind of performance from a mainstream CPU in a 65W power envelope.

Finally, the $359 Core i7-8700K brings six unlocked cores and 12 threads to the table. In the transition from i7-7700K to i7-8700K at the top of the lineup, Intel found 200 MHz more Turbo Boost frequency for lightly-threaded workloads even as it dropped two more cores into roughly the same power envelope. Compare these numbers to Intel's own $379.99 Core i7-7800X and its six Skylake Server cores, and it's clear the gap between the company's mainstream and high-end desktops is narrower than ever.

The i7-7800X is kind of the ugly duckling of the X299 platform. It doesn't have Turbo Boost Max 3.0 support like other Skylake-X chips, so it only clocks up to 4 GHz in light workloads. It has less shared L3 cache than the i7-8700K (but four times the private L2). It's limited to DDR4-2400 RAM at stock speeds, albeit four channels of it as opposed to two. The i7-7800X is also built with Intel's server-class mesh interconnect, which sometimes does not respond well to tasks like high-refresh-rate gaming. All together,  it seems that only those with a need for AVX-512 support, gobs of memory bandwidth, or 28 PCIe lanes would need to consider the 7800X for $20 more. The i7-8700K is a very potent chip, and we can say that even before we look over to the Ryzen 7 side of the aisle.

Although some will point to the lower base clocks on Intel's eighth-generation desktop CPUs as the way it held TDPs to only minor increases over seventh-gen chips, I'm not sure those base clocks will be entirely representative of real-world performance. The Core i7-8700K can sustain all-core Turbo speeds of 4.3 GHz in non-AVX workloads without a hitch, at least under the 280-mm liquid cooler we use on our test bench. That's down just 100 MHz per core from what we observed from the Core i7-7700K. Admittedly, we're looking at a 95W chip instead of 65W models, but still. Put a good cooler on these chips, and I expect the base clock could be a rare sight.