Overclocking Core i7-4790K And TIM Performance
When I first started writing for Tom’s Hardware, I was all about pushing peak overclocks at settings I knew wouldn’t last long. Anything for those big numbers, right?
Over the years, I’ve heard from too many readers with processors and graphics cards that worked great six months ago, but aren’t stable at stock settings anymore. Now, I feel that it’s more important to dial in sustainable clock rates, enjoyable under any workload. When I talk to system builders (the guys who want to overclock, but also have to honor a warranty on their configurations) the discussions get more honest and I figure out which settings are expected to hold up over time.
Core i7-4770K runs all four cores at 3.5 GHz and can get up to 3.9 GHz through Turbo Boost. Beyond those clock rates, the first batch of retail CPUs was inconsistent. Most were solid around 4.3 GHz. A great many hit 4.4 GHz. Only a few were capable of 4.5 GHz. Not surprisingly, I ended up with a sweet sample able to do 4.7 GHz. That certainly wasn’t the norm, though.
With Core i7-4790K, Intel smartly exploits much of the headroom enabled by its more effective TIM and stable power delivery right out of the box. That’s where you get a four-core 4 GHz frequency able to jump up to 4.4 GHz in lightly threaded workloads. There’s no shame in an extra 500 MHz - particularly when you consider that Core i7-4790K sells for the same price as the 4770K (it’s on pre-order right now for $340).
Of course, we still want to get more out of the processor, if we can. At a core voltage of 1.25 V (which is where we’ve settled for safety on overclocking Haswell) fully threaded workloads are fine at 4.4 GHz, while 4.7 GHz was the peak in tests like iTunes and LAME. That's where we ran our benchmarks. Pushing up to 1.31 V, though, it’s possible to run through our suite at 4.6 GHz, with single-threaded clock rates up to 4.8 GHz.
Most notable, perhaps, is that the Core i7-4790K doesn’t seem to suffer from the same quick saturation of heat that our 4770K samples experience. Rather than slamming into a throttling condition (usually brought on by too much voltage triggering untenable temperatures), we ran into the sort of crashes you can typically stave off by supplying more power to the CPU. A Prime95 burn-in might have been more troublesome, but the benchmarks we ran weren’t limited by the temperatures we were seeing.
Throughout the testing, you’ll see our stock and overclocked performance results at sustainable clock rates, representing a range of frequencies based on the test being run.
The Impact Of Intel's NGPTIM
Before we get to the bulk of our numbers, I wanted to isolate the impact of Intel's Next-Generation Polymer Thermal Interface Material. I took the Core i7-4770K and -4790K, dropped them both into MSI's Z97 Gaming 7 motherboard, applied the same 1.275 V, and manually dialed in a 4.2 GHz clock rate. For the 4770K, that's an overclock. For the 4790K, that's the factory-shipped four-core Turbo Boost setting.
Temperatures were logged in one second intervals for all four cores on each CPU, and I charted their average as soon as each processor hit 100% utilization in our 3ds Max 2013 rendering workload (in other words, this data is generated using a real-world metric).
At the same voltage and pegged at the same clock rate, Intel's Core i7-4790K runs about 6 °C cooler. Interestingly, this delta doesn't change over time (at least, not in the relatively short segments we logged thermal performance). From pretty much the moment load is applied to the processor until it's lifted, roughly six degrees separate their readings.
