Let’s start with the basic specification and some confusion. Official Intel figures show a large gap between 8400 and 8600K, but in fact the cheapest model reaches 3.8 GHz, which we confirmed on several motherboards, even with standard manufacturer cooling. 4.0 GHz boost clock speed translates into a much smaller difference compared to 4.1 GHz at 8600K, although tests in practical conditions show that it is not that close.
The Usual Options
- As always, we focus on games, but traditionally we’ve included several synthetic benchmarks to set our own expectations. Cinebench R15 is a rendering tool that calculates a complex scene using all available cores and threads, and then using only one core.
- There are a few surprises. Speaking of one core, the Coffee Lake i5 are not as fast as the 8700K, but we expected the flagship model to have a greater advantage, due to the higher turbo. The i5 results show that the 8600K equals 7700K without overclocking, and performs slightly better on many cores. This is an interesting clash of two physical cores with hyper-threading, i.e. their virtualization in 7700K this theme has been present throughout the tests. 8400 with one active core is a bit slower, but it does not differ much from 7700K if we turn them all on.
Synthetic benchmarks, therefore, suggest that the 8600K offers the i7 level from the previous generation without overclocking, while the cheaper 8400 is not far behind. Elsewhere, the twelve threads of Ryzen 5 provide an advantage, but in the single-core test it’s worse it will be similar in games. When it comes to the Motherboards for i5-8600k, now you will have to be careful in finding the best options.
Handbrake coding tests are our daily work on video content in Digital Foundry. Physical cores matter, and h.264 codecs and very demanding HVECs work more efficiently on new i5 than on 7700K. Ryzen keeps pace at h.264, but the HEVC x265 encoder already supports AVX instructions, which AMD has a problem with.
Intel
We start the game tests with the Intel family, trying to place the new i5 in the hierarchy of models of this manufacturer. We don’t feel comfortable testing the i5 8400 on the Z370 “overclocking” board, so we limit the memory to 2666 MHz (players will most likely reach for cheaper models that introduce such a limit). We add Core i5 6500 Skylake to Coffee Lake and Kaby Lake, which should be similar to 7400 from the previous generation.
As usual, we try to eliminate the variable in the form of a graphics card, betting on overclocked Titan X in Pascal architecture, operating at 1080p. The processor is responsible for the logic and preparation of instructions for the GPU, so we enable high settings to generate maximum loads. The CPU test in Ashes of the Singularity is an almost synthetic benchmark inside the game, revealing the fact that hyper-threading is still a very valuable technology. The i7 8700K processor is still in the lead, and the 7700K from the previous generation is doing very well, using four cores and eight threads beating the six-core i5 8600K.
Reverse Trend
Rise of the Tomb Raider and The Witcher 3 reverse this trend, because the 8600K gains an advantage over 7700K. Elsewhere, the differences between the two models are smaller and in our opinion the conclusions are clear. If we decided to buy from the Kaby Lake line, we still have great gaming equipment. The 7700K was and still is more than a good processor.
