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Author Topic: Cool Laptop  (Read 3160 times)

jack21

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Cool Laptop
« on: August 26, 2012, 09:30:01 AM »

I thought I'd share this with you, and pose a question too:

This is about how I made my laptop run quieter, cooler and use less electricity.

Whilst investigating why my laptop fan ran almost all of the time, I eventually discovered that it does have an alternative power mode where it runs at a reduced voltage and so produces less heat and requires less fan-cooling. In adopting this method, my own laptop, previously with fan running 80%+ of the time, now hardly ever has the fan coming on at all, and it stays much, much cooler; I don't notice any change in its performance speed - with my typical load of <10% CPU load - and the  operating frequency of the CPU remains at 1.5GHz.

The method that achieves this for my HP Compaq Presario V4215EA is:

1. Do not have mains power to the laptop when I turn it on; either disconnect the mains lead, or better, turn off the mains power switch at the wall.

2. Switch on the laptop under battery power; once the laptop has started running and a logon screen appears, I can, if I wish, turn on/connect the mains supply. It is the power-up-under-battery that is the key; removing mains supply whilst running does not have the same effect, and the effect is independent of what o/s is used.

Maybe this method will work for your laptop too.

In this reduced-power mode, the laptop heatsink naturally dissipates heat from the CPU and reaches a steady state of around 44C at <10% CPU load. If I don't follow this method, and use mains from the start, the CPU temp rises rapidly and once (approx) 57C is reached, the fan comes on and attempts to cool the CPU to below 40C, that is rapid on a cool day - on a hot day it can struggle to make the final cooling step from 41/42C to 39C. The temperature then see-saws in that 57C<>39C range with the fan being on 80% of the time.

There are no settings in its (latest) BIOS to do with power/heat/fan etc.

Question: Since I don't see a drop in CPU frequency, or notice a drop in speed performance (at my <10% load), what, if any, is the drawback in adopting this mode?

As part of the investigation, I experimented with the CPU<>heatsink interface; BTW the fan is clean and in good order and so is the heatsink.

Over a 10-day period I tried different combinations of cleaners, thermal pastes and shims - briefly summarised below - all tested under same load conditions (in the low-power mode described above):

With thermally-pasted 0.6mm copper shim in place - settles at 46C
With thermally-pasted thinner aluminium shim - 46/47C
With thermally-pasted thinner 99.9% pure silver shim - 43C
With no shim with minimal paste - 45/46C
With no shim and no paste whatsoever - very erratic - lowest temp 39C, but more/higher spikes - unable to get a 'settled' state....fluctuates 39/55 all the time
I used 3 different kinds of paste, cheap>expensive; I detected no difference in their performance.
I found that very, very minimal paste application worked best, and rubbed it in with a credit card edge.

Hope you find this informative.
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kitz

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Re: Cool Laptop
« Reply #1 on: August 26, 2012, 12:30:34 PM »

Thank you for taking the time and trouble to post your observations and results.   I hope that this will prove useful to others :)
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jack21

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Re: Cool Laptop
« Reply #2 on: August 29, 2012, 03:46:56 PM »

Update:

My Presario V4215EA was fitted with a Celeron M 1.5Ghz processor up till today, and I had read that it does not have EST (ehanced speedstep) capability (unlike the equivalent Pentium M processor). So although I can dynamically alter its CPU frequency, that doesn't alter its board voltage and heat output; that only happens at startup

So I invested in a Pentium M 1.8GHz processor (10 off Ebay) and fitted it today - results:
1. The power-on-under-battery trick isn't applicable/needed any more - even under mains-at-startup, and at its full 1.8GHz, it produces a heat output lower than the Celeron, and settles at around 7C lower than the Celeron under the same program load.
2. The Linux o/s automatically and dynamically switches the CPU frequency according to the load and  in-use cpufreq policy, and also dynamically  switches policy according to whether mains are on or off. This can result in temperatures (under battery power, or cpufreq tweaked) 10-11C lower than when using the Celeron
3. If I increase the processor load very significantly, I can cause the temperature to increase to the normal fan-on point, but in my normal <10%  load, the fan only ever comes on briefly at startup.
4. Way cooler and quieter with the Pentium than with the Celeron.
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kitz

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Re: Cool Laptop
« Reply #3 on: August 29, 2012, 09:21:00 PM »

Although my laptop is many years old now..  I know that when Im looking at laptops (ie for my daughter) then I prefer to go for the Pentium M rather than the celeron since of the main advantages is power consumption and control.   You seem to get much longer battery power from the Pentiums over the Celerons.
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jack21

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Re: Cool Laptop
« Reply #4 on: August 30, 2012, 10:57:12 AM »

Yes, Kitz, I too would plump for the Pentium in preference to the Celeron, but I note there is often a large premium to pay if buying new. I've never actually bought a new laptop myself - all broken/multiple-hand, and no more than 60, usually much less, so I'm not too picky!.  I did, however, buy a new HP DC6800 desktop 5 years ago and have been exceptionally pleased with it, especially with Linux Mint onboard in place of its original Vista.
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