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Intel Core i7-5775C 3.3GHz Broadwell LGA-1150 CPU Performance Overview

By: Steven Bassiri | Intel CPUs in CPUs, Chipsets & SoCs | Posted: Jul 2, 2015 2:13 pm



Overclocking the 5775C can be simple or challenging depending on if you really want to tweak the iGP. I would think that most people who buy the 5775C will buy it for the integrated Iris Pro graphics, and while this part of the article doesn't really cover iGP overclocking, I will show you the eDRAM multiplier.




I used MSI's Z97 Gaming 9 ACK for this part of the article. I used BIOS 1.B because it had the eDRAM multiplier in it. If you haven't flashed your Z97 board's UEFI to one of the latest, then you probably won't have this option. Intel has been pushing for microcode updates for Broadwell and I think they will make even more of an impact in the future when they are implemented.





You can overclock the eDRAM by just engaging either the 1.25x or 1.66x BLCK multiplier as the eDRAM will use the BLCK for its eventual frequency, or you can chose a multiplier like those shown above. This also means you should be careful when overclocking with BLCK, because the iGP and eDRAM frequencies are also tied to the BLCK.




The maximum overclock I was able to achieve was 4.5GHz. This means it was stable enough to validate this overclock with CPUz, but I couldn't do much else without freezing. The eDRAM addition to the system could be one reason for the lower OC, as it's the new ingredient, but I found other limits as well. Overclocking the cache and memory isn't as easy as I am used to with the 4770K and 4790K. The CPU is also pretty sensitive to voltage, too high or too low and you might get issues. I found that an Input Voltage lower than 1.9v or higher than 2.15v would result in instability. I had to use 2.0-2.1v for 4.5GHz, otherwise I was stuck at 4.4GHz. This is more of a CPU limit since I tried other motherboards, and this one was one of the best overclockers. Other media also seem to be hitting the same limits, as well.




In the end, I was able to run 4.2GHz with decent stability and 4.0GHz will full stability. In fact, I ran my entire benchmark suite at 4.0GHz with 2133MHz on the memory. It was relatively easy to overclock the memory to 2133MHz. On some Z97 motherboards, I have seen that the memory multiplier is limited to 21.33x or 28.00x, but on this MSI motherboard, it went all the way up to 32.00x. The eDRAM can overclock up to 20x multiplier and the iGPU up to 60x multiplier.


The bottom line is that you probably won't be getting the same overclocks as Haswell. That being said, you can overclock to 4.0-4.2GHz stable with a modest memory overclock, and you can overclock the iGP. You need to be careful if you use the BLCK divider, you will need reduce the multipliers, especially the cache ratio.



Power Consumption


For measuring the CPU power consumption, I used an inline DC/DC Hall Effect monitoring IC to monitor the input on the 8-pin power connector, which should be isolated for CPU use only. This is one area where the 5775C shines bright.




Broadwell and Haswell both have an integrated voltage regulator and all CPU power comes from the 8-pin. However, Ivy Bridge has some of its power coming from the 24-pin as well for the other voltage rails other than CPU and iGP. Overall, Broadwell really shines bright; its power consumption at a 200MHz lower core clock is significantly better than Haswell.




For this test, I ran the systems with the same voltage settings and frequency parameters for both the CPU and Memory and I setup the BIOS to push a 4.0GHz overclock at all times. Broadwell's idle power consumption is very low, which is a great thing considering it has that Iris Pro iGP.


At full load, it is a bit higher than the 4790K, but that is because the 4790K is a binned overclocking optimized CPU underclocked by 400MHz of its maximum turbo speed and the 5775C is overclocked 300MHz more than its maximum turbo speed. A more fair measurement of power is when the 5775C is compared to the 4770K, where there does seem to be significant power savings.

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