01-20-2013, 09:22 PM #1
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- Mar 2008
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ATIV 700 Pro Users - Does underclocking CPU extend battery life?
I'm very keen on the newer 10-13W TDP of Ivy Bridge ULV CPUs that were released at CES this month, as I think those chips might be a good compromise between performance and battery life. Normal Core i chips have too short a battery life, but good performance, and Clovertrail SoC the reverse.
Then... it just occurred to me that existing Core i chips and the newer Y-series are both Ivy Bridge, which means that their architecture is the same/very similar. Has anyone tried to underclock the CPU on the ATIV Pro to say 1.2-1.4GHz max clock speed? How does this improve the battery life of the unit? By how much?
01-20-2013, 10:19 PM #2
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Re: ATIV 700 Pro Users - Does underclocking CPU extend battery life?
To be clear, I don't own a ATIV pro, and I'm speaking from my experience with SandyBridge CPUs.
When you underclock, if you mean restricting the max clock, it could give you a bit more battery time, but I don't think it would be by much. When I had a sandybridge i5 ULV and a regular voltage i5 and compared those two, idle power usage was about the same. Also interesting was that when I restricted the max clock of the regular voltage i5 to be the same as the ULV version, power consumption was also the same.
Now let's think of two scenarios.
Scenario 1, if you are running compute intensive job, allow the cpu to ramp up. Faster clocked machine will complete earlier and go to low power idle mode. Compared to the slower ULV, you would have used about the same power (possibly a tiny more) because it finished earlier, and as a bonus you save time. This case, the faster clock the better, as long as thermals are in check.
Scenario 2, web browsing with tons of flash ads running on the background. The ULV will be the clear winner in battery life because ULV will be running at its max frequency, and even if cpu power lacks, it will just drop frames for those ads which is okay. The regular voltage cpu will be running at higher frequency the whole time using more power making those ads look prettier.
Higher frequency uses more power, and for Ultrabooks, it's more about the thermal envelope and intel's marketing rather than power savings. Unless your unit heats up a lot and you would like to rid of the heat, or as in scenario2, you do something that's not important to you constantly ramps up the cpu to its max frequency, don't bother restricting the cpu performance. Even in scenario1, you might have times you want to restrict the cpu speed though because of the heat. My Toshiba Portege R835 with a i5-2435m overheated to 100C (was perfectly fine at 40C on normal use) when it was doing compute intensive stuff, so I restricted the cpu to 90%. That got rid of most of the heat (was able to settle at 70C) while performing faster than a ULV i5.
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