Intel Core i7-6800K: Overclocking, Power & Temperatures
Base Clock Frequency, Turbo Boost & Overclocking
Intel's Core i7-6800K is its entry-level Broadwell-E model. Its base clock rate is 3.4GHz and Turbo Boost 2.0 is supposed to max out at 3.6GHz in lightly-threaded applications.
After measuring the processor's stock performance using a taxing gaming loop and full stress test, we worked to determine its highest stable overclock. Unfortunately, we hit a wall quickly, despite some extremely high voltages.
The CPU finished our stress test at 4.5GHz, but despite an extremely high 1.5V Vcore setting, that clock rate proved too aggressive for our gaming benchmark. Dropping to 4.4GHz proved helped stabilize the platform for hours at a time.
Let’s take a look at each core's frequency for the three configurations we tested:
Core Voltage Necessary for a Stable Overclock
In the end, whatever voltage is set in the BIOS only serves as a target that gets adjusted by the firmware depending on load and sensor readings. Let’s take a look at the core voltage that gave us our stable overclock.
Resulting Power Consumption
The following two graphs illustrate average power consumption during idle, gaming and stress testing. The 61W gaming measurement gives you an idea of what overclocking might look like if you want to squeeze every last bit of performance from this processor.
So what happens when the Core i7-6800K is taken to its limits? It might have stayed under the 100W mark at stock clock rates, but the CPU hits a massive 177W at 4.4GHz. The core voltage required to achieve that number is equally gargantuan.
Temperatures During Continuous Operation
So, between the massive waste heat and our high-end cooling, what do the temperatures look like? We averaged all of the cores together as reported by the sensors for each measurement interval and split them into our various workloads.
The results fluctuate according to the gaming load's variable demands. During the stress test, however, temperatures become a lot more consistent, resulting in a smooth curve.
By measuring the temperature of our water, we can see that a good open-loop solution shouldn't have any trouble keeping the Core i7-6800K cool. The CPU will destabilize long before thermal throttling becomes an issue.
Intel's Core i7-6800K is fairly efficient at its stock clock rates. At 4.0GHz, though, both power use and waste heat increase significantly. While it's possible to push this chip all the way to 4.4GHz, the resulting performance gains just aren’t worth the insane consumption at that speed.
Air cooling is really only an option if you run the -6800K at its stock frequencies. A simple closed-loop liquid cooler is needed to step up to 4.0GHz. At 4.4GHz, there’s no way around a true open-loop setup. For example, a Corsair H100i that we tried was overwhelmed after just 12 minutes, after which the processor throttled due to core temperatures in excess of 90 degrees Celsius.
The amount of waste heat generated by an overclocked Core i7-5960X is manageable. But for Broadwell-E, better heat management is a must.