Core i7-4770K Overclocking
The 4770K’s Haswell architecture re-introduces the concept of base clock overclocking, the classic overclocking mechanism which Intel removed starting with Sandy Bridge. While Intel’s press materials are (as usual) devoid of many technical details, it looks as if the CPU clock and uncore (things on the CPU that aren’t the CPU, like the iGPU, cache, etc.) clocks are now separate. This means that increasing the base clock only overclocks the CPU. In theory you should be able to significantly overclock even non-”K” CPUs, but I’ll have to wait to confirm this until I have such a CPU to test. Multiplier overclocking is still the best mechanism to use with “K”-series CPUs, since it preserve’s the CPU’s ability to clock itself down when extra performance isn’t needed. However, you can use base clock adjustments to add sub-100MHz increments to the CPU clock speed if you wish.
Enthusiasts were disappointed in the overclocking ability of the Ivy Bridge CPUs, having expected that the new 22nm fabrication processor and lower power requirements would translate into more overclocking headroom. Sadly, this did not prove to be the case. While 4.8GHz and even higher was possible on a Sandy Bridge-based Core i7-2600K CPU, Ivy Bridge was limited in my tests to 4.7GHz. Any attempts to go higher were met by temperature spikes in excess of 100 degrees Celsius, resulting in severe CPU throttling or crashes. Will Haswell be any better?
Sadly, no. With the maximum multiplier raised to 47 and a core voltage of 1.4V, I could boot into Windows, but the system would crash quickly under most benchmarks. Dropping the multiplier to 46, yielding 4.6GHz, enabled me to run most of the benchmarks, but temperatures would spike (as they did under Ivy Bridge) despite the best efforts of the Thermaltake Silver Arrow cooler with its twin 140mm fans and massive heat sink. Benchmarks like x264HD 5.0 and SPECapc Lightwave would crash the system after a minute or so.
Ultimately the highest speed I could run and still make it through my entire benchmark suite was a mere 4.5GHz; even going to 4550GHz by tweaking the base clock resulted in crashes. I was able to drop the voltage to 1.3v from 1.4v, which kept temperatures under 85 degrees Celsius even under heavy load. Given that Haswell uses the same fabrication process as Ivy Bridge, but is rated to dissipate more power (84 watts as opposed to 77 watts), the lower overclocking limits are perhaps unsurprising. But they’re still disappointing. The chart below shows the performance improvement the overclocked CPU achieved on each benchmark:
|4770K Stock||4770K OC||4770K Stock||4770K|
|OCAIDA64 Queen||1.0||1.21||x264HD Pass 1||1.0||1.15|
|AIDA64 Photoworxx||1.0||1.00||x264HD Pass 2||1.0||1.18|
|AIDA64 AES||1.0||1.22||SPECviewperf Lightwave||1.0||1.12|
|AIDA64 ZLIB||1.0||1.20||SPECviewperf Maya||1.0||1.13|
|AIDA64 Hash||1.0||1.22||SPECviewperf TCVIS||1.0||1.04|
|CINEBENCH Single Core||1.0||1.15||SPECapc Lightwave Interactive||1.0||1.15|
|CINEBENCH Multi Core||1.0||1.20||SPECapc Lightwave Multitasking||1.0||1.10|
|Handbrake 0.96||1.0||1.17||SPECapc Lightwave Rendering||1.0||1.17|
|PCMark 7 PCMarks||1.0||1.05||Blender/Icetest||1.0||1.16|
|PCMArk 7 Productivity||1.0||1.05||POV-Ray||1.0||1.18|
|PCMArk 7 Creativity||1.0||1.05||Arcsoft Media Converter||1.0||1.11|
|PCMark 7 Computation||1.0||1.16||Average Performance Improvement||13.8%|
The 13.8% average performance improvement from overclocking is considerably less than the 18% improvement returned by the overclocked 3770K. I suspect that in most real-world scenarios, an overclocked 3770K will provide performance slightly better than an overclocked 4770K.
Overclocking the iGPU was pretty easy: I was able to raise the frequency to 1600MHz from 1250MHz without a problem. Going any faster crashed the display driver, even with voltage tweaks, but the system always recovered.
|iGPU Stock FPS||iGPU OC FPS||% improvement|
|Unigine Heaven 3.0||18.1||19.6||8.3|
|Aliens vs. Predator||18.7||20.8||11.2|
|Lost Planet 2||6.7||8.0||19.4|
Average Performance Improvement
The average 19.2% improvement is a good dollop of free iGPU performance.
Overclocking the Haswell Core i7-4770K was ultimately disappointing, but better results may be possible with more exotic cooling methods. Join me in the next section for my final thoughts and conclusion.