Can Disabling Hyperthreading Increase Battery Life?

[Emberstone]

Hey there, folks. I have what is probably a really stupid question that has always been a slight curiosity of mine. My laptop is a GS63VR, and it gets around three hours of battery life outside of gaming. Could disabling hyperthreading on the i7-6700HQ yield any tangible benefit in terms of battery life?

 

Thanks for reading my dumb question!

[Mira Yurizaki]

I would say no, because if the extra bits in the CPU for Hyperthreading aren't being used, it's probably going to be shut down. HyperThread does eat up more power if something is going on, but that's about it.

 

Plus you'd have to go into BIOS every time you wanted to switch it on/off

[ARikozuM]

Probably would but you would have to factor in the performance you lose.

[kelvinhall05]

It's not a dumb question, it's an interesting one imo. I think disabling cores could increase battery life, as could switching to your igpu (if you have one) but I'm not sure disabling threads would help.

[Clanscorpia]

Nope, not at all, because hyper threading is disabled during normal use

[Godlygamer23]

Yes, because more of the cores' resources are being used, thus higher power consumption.

[corrado33]

There are programs to monitor battery draw in exact numbers. Why not download one and look at it with hyperthreading on and off?

 

I'd say yes.

[Emberstone]

Seeing a lot of mixed answers here

 

I might just have to do my own test. Play a movie with HT on and off, and see what battery life is like. I'm not too worried about the performance loss, as the games I play don't even use more than four threads anyway. I have an SSD and my boot times are less than 10 seconds, so I'm not too worried about having to turn it back on in some cases.

[Godlygamer23]

1 minute ago, Emberstone said:

Seeing a lot of mixed answers here

 

I might just have to do my own test. Play a movie with HT on and off, and see what battery life is like. I'm not too worried about the performance loss, as the games I play don't even use more than four threads anyway. I have an SSD and my boot times are less than 10 seconds, so I'm not too worried about having to turn it back on in some cases.

Here are some numbers with the 980X comparing hyper-threading on vs off. Bear in mind that the biggest difference is during CPU stressing with P95.

http://www.tomshardware.com/reviews/hyper-threading-core-i7-980x,2584-9.html

Also bear in mind that this is with an older CPU architecture  

[NuclearKing]

Can you switch over to the integrated GPU (HD 530 I believe) during non-intensive use? I believe switching over to that would make a bigger difference than hyper threading. In the NVidia Control Panel you should be able to see which programs use which GPU, or set your own depending on the program.

[Emberstone]

Just now, NuclearKing said:

Can you switch over to the integrated GPU (HD 530 I believe) during non-intensive use? I believe switching over to that would make a bigger difference than hyper threading. In the NVidia Control Panel you should be able to see which programs use which GPU, or set your own depending on the program.

I have auto-switching turned on. I'm just seeing what other gains are possible.

[NuclearKing]

1 minute ago, Emberstone said:

I have auto-switching turned on. I'm just seeing what other gains are possible.

On battery you can choose a TDP of 35w instead of 45w, just to let you know. That may help.

[Emberstone]

So here is what I did. I downloaded a program that monitors battery discharge rate, as corrado33 suggested, and ran Cinebench with Hyperthreading and without. Each test was done after a restart, so only my usual background programs will be running alongside Cinebench and BatteryInfoView.

 

While running Cinebench:

 

Without Hyperthreading, the battery discharge rate stayed right around 52 watts.

With Hyperthreading enabled, the battery discharge rate increased to 62 watts.

 

While idle:

 

Without Hyperthreading, the battery discharge rate stayed around 14 watts.

With Hyperthreading, the battery discharge rate stayed around 28 watts.

 

So Hyperthreading increased power draw by roughly 16% under a full load, and doubled it at idle according to this program. I feel like I'm missing something here, because that's a massive difference in idle power draw.

 

(I heavily edited this post after I made it, because I realized I forgot to check idle power draw. Sorry.)

[Godlygamer23]

10 minutes ago, Emberstone said:

While idle:

 

Without Hyperthreading, the battery discharge rate stayed around 14 watts.

With Hyperthreading, the battery discharge rate stayed around 28 watts.

 

So Hyperthreading increased power draw by roughly 16% under a full load, and nearly doubled it at idle according to this program. I feel like I'm missing something here, because that's a massive difference in idle power draw.

What were your clock speeds without and with hyper-threading enabled? What about CPU voltage?

[Emberstone]

Just now, Godlygamer23 said:

What were your clock speeds without and with hyper-threading enabled? What about CPU voltage?

I think I figured out the culprit. The Battle.Net client. With Hyperthreading enabled, it was taking up more CPU than many of my background processes, keeping the clock speeds well above idle.

 

Without Hyperthreading enabled, my clock speeds would hover from 1.0 to 2.0 GHz, but after enabling it the clocks stayed well above 3.0 GHz the entire time. As soon as I closed out of BNet, the clocks then mirrored my non-Hyperthreaded clocks of 1.0 to 2.0 GHz. The BNet client loves its threads I guess. The voltage then went down to around 0.8 to 1 volt or so.

 

With BNet now closed, the idle power draw both with Hyperthreading enabled and without was about 14 watts (just in case this isn't clear, I tested both HT on and off without BNet open). I wouldn't have run into this problem if I just did a clean boot, but I'm lazy and I kind of wanted these tests to simulate a realistic scenario.

 

So that means the only real factor in battery life here for the i7-6700HQ is the power draw under load, and Libre Office sure as hell isn't going to max out this processor while I'm taking notes in class.

 

Thanks for telling me to check clock speeds!