Haswell Z97 Refresh Features
Code-named "Devil's Canyon", the Intel Core i7-4790K is the K version of the equivalent Intel Core i7-4790 we previously reviewed, with the ability to not only adjust the CPU multiplier, but also the BCLK, the main clock when it comes to changing the frequency of uncore components like QuickPath interconnect and the integrated memory controller (IMC).
The newer Intel Core i7-4790K features the exact same die layout as the Intel Core i7-4770K. The processor is also built on a 22 nm process, but with a 88 W maximum TDP. Given we previously covered the specifications, there is no need to state the same information over and over again. What Intel does tout, however, is the latest 4.0 GHz base frequency. While it is nice, there is only a difference of 500 MHz overall. This may not be enough to people who are anticipating the Haswell-E.
Again, the bulk of the changes with the Z97 chipset consist of slightly faster USB 3.0 speeds, 6 Gb/s SATA ports with a speed bump, and the PCIe lanes provided by the chipset, having speeds of up to 5 GT/s (PCIe 2.0). The functionality diagram provided by Intel reveals that the PCI Express-based storage system has been upgraded to include M.2 modules (usually sold without a casing, as a plain chip-like and unshielded build by makers) that support Bluetooth functionality and more.
Compared to the Intel Core i7-4770K, the Intel Core i7-4790K also comes with new Thermal Interface Material. While a pasty gray in the past, it is now a more pasty white polymer—probably a silicone TIM. The thermal conductivity does not realistically lead to direct temperature drops of 10 degrees by default, but helps conduct a certain temperature longer on one CPU over another, here the Intel Core i7-4770K. I ran temperature tests over the length of the 100%-maximum-utilization period at the boost frequency of 4.2 GHz for both processors. These tests revealed a Delta T of 4.5 degrees Celsius. So right off the bat, the overclocked Intel Core i7-4790K is 4.5 degrees cooler than a Intel Core i7-4770K at the same frequency. The difference only seems to increase as the overclock is stepped up, which reveals something interesting we will cover in our Thermal Performance section later on.
Let's move right on to what everyone is here about: overclocking.