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Intel Core i7-8700K and i5-8400 Coffee Lake CPU Review (Page 1)

Intel Core i7-8700K and i5-8400 Coffee Lake CPU Review

Intel today takes the covers off its newest desktop processors, the Core i7-8700K and i5-8400 Coffee Lake CPUs. Strap in as we check them out.

Steven Bassiri | Oct 5, 2017 at 8:01 am CDT - 2 mins, 20 secs time to read this page
Rating: 93%Manufacturer: Intel



The day has finally come, Intel has increased the core counts of their mainstream processors, and added two extra cores to their Core i3, i5, and i7 lineup. For roughly the same price as a 7th Generation i7-7700K, you will get 6-cores and 12-threads of processing power. While there have been many unfortunate leaks revolving around Intel's 8th Generation Core processors, today we can bring you official benchmark scores with fully validated parts. We also tried our hand at overclocking the new 6-core processor, and things are looking pretty good.

Intel Core i7-8700K and i5-8400 Coffee Lake CPU Review 02 |

The new CPUs will only work in new 300-series chipset motherboards with the LGA1151 socket, and Intel says this is due to the increased power delivery requirements of the 6-core part. Recently, some leaks have shown that the pads of the CPU have changed, indicating that many reserved pins have now been activated for power delivery, so there is some merit to Intel changing the socket. Although the socket has changed, the chipset in the motherboard is pretty much a refresh of the Z270 chipset. At the moment, you will need a Z370 chipset motherboard to take full advantage of Intel's K-SKUs such as the 8700K and overclock them.

The motherboards support Intel's Optane Memory technology as well. Intel has also added more cache into the CPU and is using the 14nm++ process, which is how they are clocking up the 8700K to a 4.7GHz Turbo Boost.


Intel Core i7-8700K and i5-8400 Coffee Lake CPU Review 03 |

The i7-8700K has a base clock speed of 3.7GHz, so with all cores fully loaded it will run 3.7GHz. It also features a 4.7GHz single-core boost frequency, so a single core can boost all the way up to 4.7GHz. The i7 CPUs will feature 6 cores and 12 threads while the i5 CPUs will feature 6 cores and 6 threads. The i3 processors will feature four cores and four threads, and we don't see a 4-core 8-thread processor. The i7-8700K has a 95W TDP while the i5-8400 has a 65W TDP.

Smart Cache is now at 12MB for the i7, 9MB for the i5, and 6MB for the i3. DRAM speed is set at 2666MHz, although you will need to go into the UEFI and increase the memory multiplier to get that speed. The 8700K can overclock while the i5-8400 won't. It seems that the 8700K runs at 4.7GHz with a single core load, 4.6GHz with a double core load, 4.5GHz with a triple-core load, and 4.4GHz with a 4-5 core load, but it does run 4.3Ghz with a six-core load. Intel hasn't officially announced the clocking table though, so those are just from independent testing.


The Core i7-8700K is priced at $359 while the i5-8400 is priced at $182.

Last updated: Nov 15, 2019 at 01:16 pm CST

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Steven Bassiri

ABOUT THE AUTHOR - Steven Bassiri

Steven went from a fledgling forum reader in 2003 to one of the internet's brightest tech stars by 2010. Armed with an information systems degree, a deep understanding of circuitry, and a passion for tech, Steven (handle Sin0822) enjoys sharing his deep knowledge with others. Steven details products down to the component level to highlight seldom explained, and often misunderstood architectures. Steven is also a highly decorated overclocker with several world records.

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