Coolbook/11.6" MBA - Isn't it risky?

iRun26.2 · Feb 13, 2011

I love the thought of squeezing even more battery life out of my 11.6" MBA (although it really is pretty good already), but operating the CPU at a lower than designed voltage seems a little risky.

Has anyone had any problems using it with the 11.6" MBA? What can happen? Can you screw up your system (compromise the integrity of your data) if the lower voltage causes your CPU to hiccup?

(Maybe, as an engineer, I worry more than most because this is something that goes against good design practices)

gimmi80 · Feb 13, 2011

iRun26.2 said:
I love the thought of squeezing even more battery life out of my 11.6" MBA (although it really is pretty good already), but operating the CPU at a lower than designed voltage seems a little risky.

Has anyone had any problems using it with the 11.6" MBA? What can happen? Can you screw up your system (compromise the integrity of your data) if the lower voltage causes your CPU to hiccup?

(Maybe, as an engineer, I worry more than most because this is something that goes against good design practices)

I've coolbook since a couple of weeks. I run my 1.6ghz core 2 duo at 0.875v
I would like to go lower (0.85v) but the software does not allow it and I'm not too familiar with terminal (apparently it can be done from there).

In this forum multiple user have coolbook installed and active and no problems have been reported yet.

entatlrg · Feb 13, 2011

I have the same question as iRun plus I'm concerned about turning the fan speed down, although I could do without the roar from my 13" MBA ... my 11" doesn't get loud at all.

iRun26.2 · Feb 13, 2011

entatlrg said:
I have the same question as iRun plus I'm concerned about turning the fan speed down, although I could do without the roar from my 13" MBA ... my 11" doesn't get loud at all.

Does Coolbook let you control the fan too (or does that require additional software)?

Additionally: You bring up an often not mentioned advantage of the 11.6" vs the 13.3" MBA: Quieter (and cooler....I like both!) I think I will be biased towards getting ULV processors in the future.

bshaf1 · Feb 13, 2011

the worst case scenario from what i've read is that your computer starts having kernel panics if it's undervolted..

..increase the voltage and then you should be good

iRun26.2 · Feb 13, 2011

bshaf1 said:
the worst case scenario from what i've read is that your computer starts having kernel panics if it's undervolted..

..increase the voltage and then you should be good

Will you lose all of your unsaved data when you get a kernel panic?
(Is that like the 'blue screen of death' in MS Vista?)

jrabbit · Feb 13, 2011

iRun26.2 said:
Will you lose all of your unsaved data when you get a kernel panic?
(Is that like the 'blue screen of death' in MS Vista?)

Yes.

iRun26.2 said:
Does Coolbook let you control the fan too (or does that require additional software)?

No, you need separate software.

Note that you don't really want to limit the fan speed (if you do, and screw it up, you can cook your system). The reason to run fan control software is to change the default thresholds. Most people can increase the default fan speed a bit without noticing a change in sound level. This results in keeping the CPU cooler longer: it takes more fan noise to cool down a hot CPU than it does to keep it cool in the first place.

I posted this a while back...

jrabbit said:
Each CPU core behaves in a unique way; the factory defaults are set with fairly generous tolerances. The key to using CoolBook effectively is:
Find the "magic" pairs: a. Lowest voltage for highest frequency the chip supports; b. Highest frequency for the lowest voltage the chip supports
Once you find the "magic" pairs, you can set a number of "in between" voltage/frequency pairs

Keep in mind that heat (power) is generated linearly with the frequency and with the square of the voltage, so that's why managing both is important; that's also why focusing on voltage is key. The formula is P = C x V^2 x F (Power/Capacitance/Voltage/Frequency).

For my system, this is what I found/use:

CoolBook settings:

MBA 1.8GHz 128GB SSD

Adapter:
800MHz 0.9000V
1200MHz 0.9000V
1400MHz 0.9000V
1600MHz 0.9000V
1800MHz 0.9625V

Battery:
600MHz 0.9000V
800MHz 0.9000V
1200MHz 0.9000V
1600MHz 0.9000V
1800MHz 0.9625V

Throttling level: High
Thermal limit: 85C

"Base" Pairs (found by testing):
1600MHz 0.9000V [highest frequency for lowest voltage]
1800MHz 0.9625V [lowest voltage for highest frequency]

I then set smcFanControl to keep the minimum fan speed at 1800rpm when on battery, and 3200rpm on A/C. Those exceed the default minimum speeds, but it's far easier for the system to stay cool than to get hot and cool back down. I chose those speeds because they are just barely audible (to me; your ears may be better or worse).

gimmi80 · Feb 13, 2011

jrabbit said:
I posted this a while back...

You keep fairly high voltage for your processor.
I've a 1.6GHz and it runs on 0.875v at all speed

I keep:
A/C
1200 MHz 0.875v
1400 MHz 0.875v
1600 MHz 0.875v

Battery
600MHz 0.875v
1600 MHz 0.875v

Throttling Medium

gimmi80 · Feb 13, 2011

I've actually looked around and it seems that keeping the settings too low might worsen battery life.
I'm confused.

aleni · Feb 14, 2011

i use coolbook on my 1.4Ghz 11" air, i can get 6.5-7 hours of daily usage with that.

the setting for all clocks is 0.875v

jrabbit · Feb 14, 2011

gimmi80 said:
You keep fairly high voltage for your processor.
I've a 1.6GHz and it runs on 0.875v at all speed

I keep:
A/C
1200 MHz 0.875v
1400 MHz 0.875v
1600 MHz 0.875v

Battery
600MHz 0.875v
1600 MHz 0.875v

Throttling Medium

I don't really have a choice on the voltages... I tested everything, and what I posted is the best the CPU in my MBA will do reliably; the tests generate kernel panics with lower voltages at the higher frequencies. You must have gotten luckier than me in the CPU lottery!

omniatlas · Feb 14, 2011

jrabbit said:
I don't really have a choice on the voltages... I tested everything, and what I posted is the best the CPU in my MBA will do reliably; the tests generate kernel panics with lower voltages at the higher frequencies. You must have gotten luckier than me in the CPU lottery!

Perhaps the 1.6 ghz processors are more stable than the 1.8?

I've been reading - the macbook air 1.6 doesn't seem to have problem reducing the voltage to 0.875

Just found a good writeup of the program -- http://gigaom.com/apple/fix-macbook-air-streaming-video-and-overheating-problems/

I might take the gamble and spend the $10.0.

DarwinOSX · Feb 14, 2011

Its risky. Don't do it.

gimmi80 · Feb 14, 2011

jrabbit said:
I don't really have a choice on the voltages... I tested everything, and what I posted is the best the CPU in my MBA will do reliably; the tests generate kernel panics with lower voltages at the higher frequencies. You must have gotten luckier than me in the CPU lottery!

In another thread of this forum I found several MBA 13' user that have similar settings...The most preforming processor might be more demanding... who knows?

Anyway my question remains the same, both you and the girl in the link posted above (Jenny Kortina) use many setting at high throttling.
I use two settings only at low throttling (at least in battery power mode).

My rationale was that when I don't need power I want to use the processor at the lowest frequency available and, when I need more power, switch to the highest setting.

This, of course, changes based on the type of workload that is done on the MBA, but in my case I mostly use the MBA as sort of typing machine (requiring low performance). Sometimes I use Aperture and the processor bumps up to 1600MHz and stays there all the time.

I don't know... I need more feedback

gimmi80 · Feb 14, 2011

jrabbit said:
I don't really have a choice on the voltages... I tested everything, and what I posted is the best the CPU in my MBA will do reliably; the tests generate kernel panics with lower voltages at the higher frequencies. You must have gotten luckier than me in the CPU lottery!

By the way, if you are talking about the MBA that is in your signature, the rev A model, that's a complete different animal, therefore our settings are not comparable.

Even the new 1.8GHz processor is different compared to the rev A.

Your settings are inline with the one that other rev A user adopted.

kryca · Feb 14, 2011

DarwinOSX said:
Its risky. Don't do it.

It isn't risky. Do it. Unless you give some concrete evidence besides the ubiquitous "Apple knows best what is good for you".

The $10 are the best I spent on the MBA.

aleni · Feb 14, 2011

gimmi80 said:
You keep fairly high voltage for your processor.
I've a 1.6GHz and it runs on 0.875v at all speed

I keep:
A/C
1200 MHz 0.875v
1400 MHz 0.875v
1600 MHz 0.875v

Battery
600MHz 0.875v
1600 MHz 0.875v

Throttling Medium

why did u remove the 1.2 and 1.4ghz settings? removing those clocks will result in decrease battery life, when you are doing some task that needs only 1.2 ghz, it will run in 1.6ghz thus decreasing battery life.

gimmi80 · Feb 14, 2011

aleni said:
why did u remove the 1.2 and 1.4ghz settings? removing those clocks will result in decrease battery life, when you are doing some task that needs only 1.2 ghz, it will run in 1.6ghz thus decreasing battery life.

I followed the recommendation of somebody on this forum.
The rationale is to have the CPU work at 600MHz most of the time and bump up to 1600MHz only when needed.

I've heard the argue that forcing the CPU to work on low frequency (600MHz) when it actually needs more power, could achieve the opposite effect (I mean use more battery).

Mac32 · Feb 14, 2011

OK. Quick answer:
I've used Coolbook for several years on several macs, no problems. With Coolbookcontroller your CPU will live longer if anything (less heat).
Use the lowest volt settings on all the stock CPU frequencies. Don't change the stock CPU frequencies (Don't use 600mhz, too slow!). Also, use "high" throttle.

If you get kernel panicks, just use a higher voltage setting, - but *by far* most likely your MBA 11.6 will work flawlessly.

impulse462 · Feb 14, 2011

DarwinOSX said:
Its risky. Don't do it.

It's only risky for people who don't know any better.

Instead of just doing what apple thinks is best for you, you could think, "hey, lowering the voltage for anything means less heat and less power,"

The worst that could come out of lower voltages is you'll get a kernel panic. You boot up again and revert to the older voltage.

Raising the voltage to overclock a cpu is the risky business.

2IS · Feb 14, 2011

DarwinOSX said:
Its risky. Don't do it.

And you're basing this off what? If you're going to make a claim, at least back it up with something.

Back on topic:

Coolbook does not adjust fan speed, and as mentioned previously, you don't want to. However, one of the benefits of coolbook is that lower fan speed is an automatic byproduct of using it. Lowering the CPU voltage serves multiple purposes.

1) It gives you greater battery life, particularly under load situations.
2) CPU runs cooler due to lower voltage and due to this reason, the fan rarely if ever ramps up to its full speed simple because it doesn't need to.

The down side is that if you go to low or if you have a CPU that just isn't as good as some other ones, you may get instability. Just start off with small steps, meaning, don't just pick .875v across the board. Just because it worked for someone else doesn't necessarily mean it will work for you. I'd start by pushing a bit more voltage than that for the higher frequencies and just go from there.

drxcm · Feb 14, 2011

My experience with the 1.6 is very positive.
Lowest voltage for all clock speeds, no kernel panics under heavy load.
Also I'm getting around an extra hour of battery life under normal loads / usage (around 6 hours).

Those that say it is risky clearly haven't tried it, or don't know what they are talking about.

gimmi80 · Feb 14, 2011

Mac32 said:
OK. Quick answer:
I've used Coolbook for several years on several macs, no problems. With Coolbookcontroller your CPU will live longer if anything (less heat).
Use the lowest volt settings on all the stock CPU frequencies. Don't change the stock CPU frequencies (Don't use 600mhz, too slow!). Also, use "high" throttle.

If you get kernel panicks, just use a higher voltage setting, - but *by far* most likely your MBA 11.6 will work flawlessly.

Thanks. I'll follow your recommendation.

iRun26.2 · Feb 14, 2011

drxcm said:
My experience with the 1.6 is very positive.
Lowest voltage for all clock speeds, no kernel panics under heavy load.
Also I'm getting around an extra hour of battery life under normal loads / usage (around 6 hours).

Those that say it is risky clearly haven't tried it, or don't know what they are talking about.

You have convinced me! I think that I am going to buy it and try it (though it kind of goes against my engineering intuition).

It makes sense, though, that that the 1.6MHz machine would be better at dealing with lower voltages that the 13.3" model chips. The ULV chips were probably picked out as being 'special' in that they worked better at lower voltages while the other chips did not. I suspect that the chips really aren't physically any different: they just passed tests that the other chips did not (hence the higher price from Intel).

(Sort of like normal ICs that are rated for either Commercial, Industrial, or Military temperature ranges with Military temperature versions costing the most)

omniatlas · Feb 14, 2011

I bought it -- currently underclocked all cpu frequencies to 0.875. Will post my battery lifespan when I'm done playing with it -- anyone know if B/2 should be checked? It halves the bus speed.

Coolbook/11.6" MBA - Isn't it risky?

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