Legit Reviews

Posted: **Fri Jun 14, 2013 7:56 am**

What Enabling C6/C7 Low-Power States Do on the Core i7-4770K Haswell CPU

Intel’s 4th Generation Core series processors have been out for a couple weeks and we have had a chance to better look at Haswell’s C6/C7 low-power states. This is a power saving feature that will help reduce temperatures and lower power consumption, but sadly most motherboard vendors have chosen to disable C6/C7 by default in the BIOS. Read on to see what happens when we enable it on the Intel Desktop Board DZ87KLT-75K with the Core i7-4770K processor

On our Windows 8 test platform we were able to quickly see the benefits of running with the C6 and C7 power states enabled. We found that with C6/C7 disabled that the system would idle between 23.7 and 24.1 Watts, but with them enabled we were seeing between 20.5 to 21.2 Watts. Both numbers are impressive as you have to keep in mind that the whole system is being measures here with a Kill-A-Watt power meter at the wall outlet

Article Title: What Enabling C6/C7 Low-Power States Do on the Core i7-4770K
Article URL: http://www.legitreviews.com/article/2217/1/

Posted: **Fri Jun 14, 2013 8:18 am**

A ~3W reduction in power?

Really? I expected more...

Posted: **Fri Jun 14, 2013 8:50 am**

I was expecting no more than 5W as back in May the PSU companies released PR's like this: http://forums.legitreviews.com/about44877.html

There has been a lot of talk about PSU compatibility for Intel’s upcoming 4th Generation Core Processors (code named Haswell). We have observed a large amount of misinformation being spread. We would like to clarify the situation to calm and below are some quick facts that the public should be aware.

- Most power supplies don’t support Haswell – False
- I need a Haswell certified power supply to build a Haswell system – False
- Haswell only works with DC-DC Power Supplies – False
- Haswell only works with 80+ Gold and better Power Supplies – False
- Haswell requires a second 12V rail and doesn’t work with single rail Power Supplies – False
- On some older power supplies, Haswell consumes 5W more in idle mode - True

So, in a sense they are saying that without C6/C7 support that you'd see about 5 Watts more at idle. I was seeing about 3W more, but was using a supported PSU.

Posted: **Fri Jun 14, 2013 4:28 pm**

Is it worth it? Nah. Surely anyone who bought THAT board would not even care about a 3W idle power drop

But since when is it worth it? ... My Nehalem Xeon L5520 goes into C6 drawing ... 0.8W on 12V2

Sure my EX58-UD5 mobo is not exactly power efficient but it stands

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