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Intel Core i5-6600K (Skylake) review

Our Rating :
Price when reviewed : £228
inc. VAT

Modest CPU and GPU gains over the previous generation, but Skylake is as future-proof as it gets right now


Socket: LGA 1151, Cores: 4, Frequency (boost): 3.5GHz, Integrated graphics: Intel HD Graphics 530



Intel was notoriously against overclocking in the past, keeping processors as locked down as possible. That has slowly changed over the past decade, with multiplier overclocking available on the enthusiast level K chips and ratio-based Base Clock (BCLK) overclocking introduced with Haswell in 2013. Skylake takes things even further, allowing complete control over the BCLK. As this clock is no longer tied to SATA and PCI-Express timings, you should be able to squeeze the absolute most out of each CPU without risking data or video corruption by sending SATA or PCI timings out of whack.

That being said, we weren’t able to see many gains from pushing the Base Clock. Increasing it by even a few MHz led to instability and crashes until we started boosting the CPU voltage. We had more luck by increasing the multiplier, easily pushing the i5-6600K to 4.5GHz at maximum Turbo speeds without needing to adjust voltages. This gave a significant boost in our multimedia benchmarks, producing a fantastic overall score of 146. We pushed the chip further to 4.7GHz for a slightly faster 148 total, but we had to increase voltages to beyond 1.35v to keep the chip stable. We’ll need more time with Skylake in order to see how base clock settings can squeeze extra performance from the architecture.

Intel Skylake processor benchmarks - overclocking

Thermals and power consumption

Overclocking dramatically increased power consumption too; our reference system, fitted with an i5-6600K, two sticks of DDR4 RAM and an M.2 SSD, typically draws 29w at idle and 80w under load, but these figures jump up to 49w and 130w respectively. Skylake might use the same 14nm process as Broadwell, but out-of-box power requirements are considerably higher too. Whereas desktop-based Broadwell chips had a 65W Thermal Design Point, the maximum amount of heat generated by the CPU that the cooling system has to dissipate, the i5-6600K has a 91W TDP.

Sadly, Intel didn’t provide us with the new stock heatsink that will come bundled with all 6th-generation Core processors, so we used a third party cooler, the BeQuiet Dark Rock Pro 3. This monstrous two fan tower cooler kept the i5-6600K at a very cool 28C at idle.

Intel Core i5-6600K rear core

Should you upgrade?

There’s no doubt Skylake is a powerful platform, and although it isn’t quite as power-efficient as the Broadwell architecture that came before, it will be arriving in much greater numbers and have much greater support from motherboard manufacturers. The Core i5-6600K in particular looks like an excellent buy, whether you plan on overclocking or not; it’s faster than previous generation Intel chips at stock speeds, beats AMD for graphics performance for the first time and uses a modern chipset that supports plenty of new and upcoming technologies like U.2 and PCI-express-based storage.

However, it will be an expensive upgrade. Not only do you have to consider the price of the processor, but also factor in the cost of a motherboard and, with all current boards, a set of DDR4 memory. Thankfully the latter is no longer quite as expensive as it was last year, but it’s still nowhere near as simple as simply dropping a new chip into your existing system and flashing a BIOS update.

Haswell owners will only see modest gains for an expensive initial outlay, but if you’ve been holding off upgrading for coming up to five years, Skylake is the perfect opportunity to overhaul your PC. 

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SocketLGA 1151
Frequency (boost)3.5GHz
External bus100MHz
Level 1 cache4x 32KB
Level 2 cache4x 256KB
Level 3 cache6MB
Supported memory typeDDR4/DDR3L
Power rating (TDP)91W
Integrated graphicsIntel HD Graphics 530

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