Intel Core i7 8700K / i5 8600K / i5 8400 'Coffee Lake' review: affordable six cores!

More cores for the same price!


The platform: Z370

The new Coffee Lake processors use the exact same Socket 1151 processor socket as the Skylake and Kaby Lake generation processors. This means that theoretically Coffee Lake chips should work on existing motherboards... unfortunately this is only in theory, in practice we see something different. 

This week we also saw the introduction of a new chipset by Intel. This Intel Z370 is the successor of Z270; if you want to use Coffee Lake you need a new motherboard with that new chipset. 

When asked for the reason for this, Intel reported that the increase to six cores from four cores means that the power supply of existing motherboards could be insufficient; Intel could not guarantee that the new processors would work on all existing motherboards. Fair enough, but this does not explain why you would need a new motherboard for the new Core i3s; it also does not explain why the compatibility does not work the other way around either: a Kaby Lake processor does not function in a Z370 motherboard. 

As far as we can check the Z370 chip is physically identical to its predecessor; the characteristics are the same as well. Like the Z270, the Z370 offers 30 flexible I/O-lanes. The motherboard manufacturers can use a maximum of 10 for USB 3.0, a maximum of 24 for PCI-Express 3.0 lanes and a maximum of six for SATA600-connectors. Aside from that, the chipset also offers support for USB 2.0, HD Audio and multiple (legacy) protocols. While the big amount of PCIe-lanes is a big plus (and ideal if you want to connect multiple modern SSDs), the fact that Intel introduces a chipset without integrated USB 3.1 gen 2 is painful anno 2017. Motherboard manufacturers still have to use separate controller chips. The same goes for Thunderbolt 3.0. 

That the chipset is not exactly new, does not mean that the motherboards are not new either. All motherboard manufacturers are releasing multiple Z370-models, that are clearly different than their Z270-models of last year. Of course all of the new motherboards can be used in conjunction with the six-core CPUs. They are equipped with the latest generation extra controller chips. In a separate article we will cover the first batch of new boards that entered our test lab. 

In time Intel will also introduce H370 and B310 chipsets for cheaper motherboards for the 8th generation Core-processors. Late next year should also see the introduction of a more luxurious Z390 variant, but what we can expect of that is still shrouded. 


three products discussed in this review

  Product Lowest price

Intel Core i5 8400 Boxed

Socket 1151, 2.8 GHz, 6 cores, 65 W, 14 nm, Integrated graphics

Specifications Test results Reviews Prices


Avg. £209.99
8 shops, 5x stock

Intel Core i5 8600K Boxed

Socket 1151, 3.6 GHz, 6 cores, 95 W, 14 nm, Integrated graphics

Specifications Test results Reviews Prices


Avg. £274.97
7 shops, 6x stock

Intel Core i7 8700K Boxed

Socket 1151, 3.7 GHz, 6 cores, 95 W, 14 nm, Integrated graphics

Specifications Test results Reviews Prices


Avg. £420.00
8 shops, 6x stock

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