CPU and Windows Power Saving Features vs Performance & Responsiveness

I was orginally just gonna post this in my thread where I have my build logged (the desktop PC in my sig), but I figured why not start a new thread for this. I've been doing some experiments with Power Saving features to see their effect on performance & responsiveness. My aim was to allow my overclocked CPU to downclock and/or reduce voltage while idle to both reduce power usage but also to allow for a long life for the CPU while still retaining maximum performance and a snappy responsive system. My conclusion from testing: use Windows High Performance Power Plan and have C-states enabled in your BIOS.

Here's the testing & reasoning:

Spoiler: Testing & Results

Variables tested:
-Windows Power Plan settings
-C-States enabled/disabled
-Speed Shift enabled/disabled

Configurations tested
A) Windows Balanced Power Profile / C-states disabled (my initial configuration historically)
B) Windows High Performance Power Plan / C-states enabled down to Package C6 (cores enter C7) (end result is that frequency locked at 4.5Ghz yet voltages lower at idle).
C) Windows High Performance Power Plan / C-states disabled / SpeedShift enabled by using Throttlestop program @EPP=78

Tests run:
-various game benchmarks
-various synthetics like CinebenchR15 and 3DMark
-PCMark 8

Results:
Gaming benchmarks and synthetic tests didn't really show a statistical difference between the results of the different configurations above so we'll ignore those and focus on how responsive & snappy the computer might feel to use under the different configurations - as measured by PCMark 8. Here are the PCMark 8 results from the Home Test:
A) Windows Balanced Power Profile / C-states disabled = 4910
http://www.3dmark.com/pcm8hm3/314687
B) Windows High Performance Power Plan / C-states enabled = 5176, 5185
http://www.3dmark.com/pcm8hm3/314646
http://www.3dmark.com/pcm8hm3/314722
C) Windows High Performance Power Plan / C-states disabled / SpeedShift enabled @EPP78 = 4934, 4925
http://www.3dmark.com/pcm8hm3/314625
http://www.3dmark.com/pcm8hm3/314700

Power usage measured at idle using KillaWatt for Option B (C-states enabled) = 42W, which is 6W lower than Option A or C. (20W extra is used if no power saving features are used at all - when CPU is locked at 4.5Ghz and 1.3V - Windows High Performance Power Plan, but with C-states disabled - that config not listed above & not tested extensively.)

As you can see Option B was the best performing option (while also having the lowest idle power consumption), I ran some of the tests twice, and each test by default consists of 3 runs, so the results are reproducible and good. The Option B score is 5% higher than the speedshift version. Also my testing shows idle system wattage is 6W less using Option B too (in comparison to both Option A and Option B). At this point I'd say that C-states are more effective than speedshift in terms of performance & also energy efficiency. (Option B enables my CPU to stay locked at 4.5Ghz, but the voltage drops when idle - the voltage drop when idle was my main goal, while still retaining maximum performance).

I hope this info might be of use to anyone else who is looking for maximum performance from their CPU while still wanting to have power saving & CPU life saving features enabled. My advice is to use Windows High Performance Power Plan and have C-states enabled in your BIOS.

I hope you people find some use in this if you're also looking to fine tune your CPU performance. Would be interesting to hear your thoughts & what configurations you run with, and your own experiences in relation to this.

 

More info for you. If you haven't seen it before.
Skylake – Overclocking – Power Consumption and Voltage Scaling

 

Woohoo, first reply to this thread! Thanks for the info, I'll check it out later, have to get off to work now! Will edit this post with anything interesting re article later.

 

@Papusan , was gonna read your article, but the link's not working? Saying "Database Error"

 

Strange. Clicked on it now. Working as intended. I expect you as well use Chrome. Tested also with Safari. Try again bruh.

 

Ah, it's working now! I read the article, although I disagree with his conclusion to disable C-states & rely on speedstep: my testing on my rig shows that C-state enabled along with High Performance Power Plan (essentially speedstep disabled) gives the best performance while having a really low idle power consumption, as I type this my PC (minus the monitor) is only using 41W). His article did give me an idea though, I might try a different mode of overclocking, at the moment I'm using Offset Mode because when I set up my overclock I was using the Windows Balanced Profile and I wanted my CPU to downclock at idle - now that I know that C-states + Windows High Performance Power Plan (CPU doesn't downclock) is the best combination, then I might try using a fixed voltage mode. I'm hoping using this different method of overclocking will allow less voltage to be used for any given overclock - in which case I'll bump my CPU back up to 4.6Ghz or higher as long as voltage is not above 1.3V.

EDIT: nope, I tried, can't overclock any higher using fixed voltage, and idle power usage went up 10W by using that method. I manually set voltage to 1.3V and then tried 4.7Ghz, it booted but failed immediately on OCCT. I know 1.3V is good for 4.6Ghz for pretty much all cases, even 8hrs of Prime95, but that setting fails an hour long test of OCCT. Seeing as I don't want to use more than 1.3V I'm gonna have to stay on 4.5Ghz.

 

I know this is old but did you have a chance to test Windows High Performance vs EPP 0?


Sent from my iPhone using Tapatalk

 

Hi, I didn't test EPP 0 thoroughly, but I do remember enabling EPP 0 to see what the general effects were on CPU frequency. If I remember correctly EPP 0 made the CPU stay at max turbo most of the time, with occasional short drops to lower frequencies, so I quickly discounted EPP 0 as a viable setting.

 

In my case my i7-7700HQ always stays in turbo speeds in Windows High Performance as well as EPP 0. I have not seen my cpu going to base multipliers in High Performance or EPP 0.

 

Not much point in using EPP 0 then, because you're not getting power savings in that case. C-states enabled & Windows High Performance power plan is my preferred combination.

 

Is speed shift not using c-states?

 

Speed Shift is just a feature of Skylake CPUs (and maybe Kaby Lake, not sure about Kaby Lake) where the CPU controls it's own frequency based on the work load incoming to it. It is more efficient than using the Balanced Power Profile in Windows to control CPU frequency, because the CPU knows best about which state it needs to be in & can respond faster with lower latency, whereas CPU frequency control through the OS is slow & more innefficient. C-states are seperate & different to Speed Shift - C-states just allow parts of the CPU to go to sleep & enter lower power states when workload is low - the frequency is not being changed here, just parts being put to sleep.