Disabling cores on quad core laptop for better battery life?

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Batman

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#207758 12-Jan-2017 14:38

Hi I have a 4702HQ laptop with 37W TDP. When on battery I only use it to browse the web, and watch youtube.

In theory, which of these 2 would give lower power consumption?

1. Limit 4 cores to 85% of max speed, lowering V by .2V

2. Use only 2 cores without limiting speed.

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#1702090 12-Jan-2017 14:42

Lol in trying to answer my own question, I've decided to try it on 1 + 2 ... :)

No difference in usage experience. I might need to remember to activate some cores when I want to do intensive stuff lol

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#1702126 12-Jan-2017 15:35

I suspect turboboost and Speedstep will over-rule manual restrictions - Tiz what they are there for

C1 state (HALT) that that CPU supports looks like it does just that?...

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#1702135 12-Jan-2017 15:45

In Windows power options, choosing the 'Balanced' profile instead of 'High Performance' will throttle back your CPU.

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#1702137 12-Jan-2017 15:52

Oblivian:

I suspect turboboost and Speedstep will over-rule manual restrictions - Tiz what they are there for

Haha, nope

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#1702138 12-Jan-2017 15:53

yitz: In Windows power options, choosing the 'Balanced' profile instead of 'High Performance' will throttle back your CPU.

Actually in default balanced profile no it doesn't, but one can tweak it

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#1702139 12-Jan-2017 15:54

joker97:

Oblivian:

I suspect turboboost and Speedstep will over-rule manual restrictions - Tiz what they are there for

Haha, nope

As in, you disable a couple of cores. The other features are surely going to switch off and run the remaining ones at full speed as you have just halved their efficiency thus negating any such saving

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#1702140 12-Jan-2017 15:57

Use the power save profile option in windows power settings if you need to save battery. My laptop has a I5 4200M and this mode limits it to 800MHZ both cores. This is fine for browsing and even MS Office but anything more and you need to turn it off again. If windows update decides to run while its enabled then the machine will chug too.

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#1702141 12-Jan-2017 15:57

Oblivian:

joker97:

Oblivian:

I suspect turboboost and Speedstep will over-rule manual restrictions - Tiz what they are there for

Haha, nope

As in, you disable a couple of cores. The other features are surely going to switch off and run the remaining ones at full speed as you have just halved their efficiency thus negating any such saving

Oh I see what you mean. I will check the Voltage steps. THanks. Many many apologies

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#1702144 12-Jan-2017 16:04

voltages have come right down with 2 cores! about 20-30% less! and yes stepping down and throttling appropriately and even much lower when idling away. though apparently not the heat side because the fan is going berserk. (maybe 2 cores work harder than 4, or the stupid windows is doing something behind my back again)

now if only there was a way to use 2 cores on battery and 4 when plugged in ...

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#1702183 12-Jan-2017 17:51

Gone back to quad core because temps were 10C higher with 2 cores, but mainly the fans that drove me berserk

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#1702191 12-Jan-2017 18:41

Power/thermal controls are largely preset within the system BIOS, so unless you can get a custom BIOS tweak from your system manufacturer... difficult even for retail ASUS etc. motherboards.

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#1702202 12-Jan-2017 19:23

Disabling a core likely wont achieve anything much at a guess. From memory The speed of a CPU is governed by the voltage supplied to it, and thus the TDP. I think the terms for each voltage level (and frequency) is called a P-state, and when the processor/core/thread is idle its called a C-state.

Speedstep allows the OS to control the P-State, and SpeedShift is the hardware equiv. when the thread/core/processor becomes idle it can drop into a c-state to save power, the depth of which can be varied. Depending on the (intel) processor there can be other technologies involved such as PAIR And PECI.

In windows, there is another power plan under balanced called 'power saver'

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#1702320 12-Jan-2017 23:35

joker97:
Hi I have a 4702HQ laptop with 37W TDP. When on battery I only use it to browse the web, and watch youtube.

In theory, which of these 2 would give lower power consumption?

1. Limit 4 cores to 85% of max speed, lowering V by .2V

2. Use only 2 cores without limiting speed.

Or #3 do nothing may be more efficient than both above.

I don't know but I'm sure it depends on the type of workload.

Screen brightness etc could have a larger effect.

I wonder if clocking down the graphics or reducing graphics chip set features could make a dent?

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#1702321 12-Jan-2017 23:38

Does YouTube use h264 by default? There is an extension for it. That might be interesting. Offloads to GPU more efficient in theory is the claim.

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#1702323 12-Jan-2017 23:39

Disable JavaScript. I guarantee you some CPU back.

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