Vital Signs and Overclocking
Below are a couple of screenshots from the latest version of CPU-Z that detail some of the new Core i7-4770K processor’s inner-workings.
As you can see, the Core i7-4770K utilizes the new socket 1150, it's built using Intel’s 22nm process node, and has a TDP (Thermal Design Power) rating of just 84w. The chip we tested, and that will hit retail shelves, is stepping 3 and it features a stock 100MHz BCLK, which is incorrectly labeled bus speed in the first image above.
Because HyperThreading is supported and enabled, the Core i7-4770K can process up to 8 threads simultaneously on its 4 physical cores. Like previous generation Intel processors, SpeedStep and Turbo boost technologies are leveraged in the Core i7-4770K (and other 4th Gen Core family of processors) that dynamically adjusts the CPU frequency up or down based on load. While idling, the Core i7-4770K frequency will step, but its base clock is 3.5GHz (35x100) and it can Turbo up to 3.9GHz (39x100) under load, power and thermals permitting.
The Core i7-4770K has 8MB of 16-way set associative Level 3 / LLC cache, which is shared amongst the CPU and graphics cores. The chip also has 1MB of L2 cache (4 x 256K, 8-way set associative) and 128K (4x32K) of L1 Data and 128K (4x32K) of L1 Instruction cache. The 128MB eDRAM cache that will be enabled on some 4th Gen Haswell based processors is not listed here.
Like the Ivy Bridge-based third generation Intel Core processors, new Haswell-based processors offer limited flexibility when overclocking via BCLK manipulation. If you want to tweak CPU and memory frequencies via the BCLK, it can only be increased by a few MHz at a time. Intel claims about 4-%-7% in either direction, but that’s just a rough guideline--we've seen some go higher and some go lower. With Haswell, however, additional BCLK multipliers or straps are also available. So, while you only have a few MHz in each direction to change the BCLK, the additional straps--which will be available on K-SKUs only--give users the ability to set the BCLK to 100MHz, 125MHz, 167MHz, or 250MHz.
Also like previous-gen Intel Core processors, different product families based on Haswell have differing overclocking options enabled. K-series SKUs, like the Core i7-4770K we’re featuring here, are unlocked for easy overclocking via multiplier or BCLK strap manipulation. But non-K SKUs will have “limited” unlocking which will allow for multipliers to be increased by up to 4 speed bins above the processor’s peak, official Turbo frequency. And processors that don’t offer Turbo, can only be overclocked by altering the BCLK. Now, while there’s not nearly as much BCLK headroom as previous architectures, that doesn’t mean it can’t be altered at all. As we’ve mentioned, there’s a bit of wiggle room there. As far as the other overclocking related features go, 4th Gen Core processors also support the latest XMP memory reference code.
We spent some time tweaking our Core i7-4770K using the stock Intel PIB cooler and an Intel's own DZ87KLT-75K motherboard and were easily able to hit a rock-solid and perfectly stable peak frequency of 4.41GHz. We achieved this speed by increasing the CPU voltage by .19v, with a multiplier of 44 and a BCLK of 100.17MHz. With more tweaking, we're certain higher clocks will be possible.
We were actually able to boot into Windows and run benchmarks at clocks above 4.6GHz, but our CPU was breaking the 90’C mark, throttling to keep temperatures in check, and almost immediately throwing a blue screen. We should also mention that at the speeds we hit, with the stock cooler, temperatures were not an issue. While overclocked using a stock cooler, the 4770K idled in the high 40'C range and peaked in the low 80'C range. With such a small die though, thermal density will likely be an issue for overclockers. If you plan to overclock a Haswell chip, despite their relatively low-power consumption characteristics, you'll need a highly efficient cooler to pull heat away from the chip as fast as possible. We should also note that 4th Gen Core processors are using the same TIM between its integrated heat spreader and the surface of the chip as Ivy Bridge, which isn't terribly high performing.
While we had the chip overclocked, we ran the multi-threaded Cinebench R11.5 benchmark to illustrate the kind of performance gains possible and were able to increase performance from the Core i7-4770K’s stock score of 7.91 to an impressive 8.77. The higher clocks we were able to achieve on the overclocked Core i7-4770K almost allowed it to overcome the two-core advantage of the Core i7-990X, but not quite.
We also monitored out test system's power consumption while we had the Core i7-4770K overclocked and saw a relatively small increase in power consumption. The additional 500MHz over stock we were able to achieve resulted in an increase in power consumption of about 22W.