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View Full Version : CoolBook/Rev B: Lowest voltage across entire frequency range?




Esopus
Jan 7, 2010, 12:12 PM
I installed CoolBook on my mom's MBA Rev B 1.86/SSD and it appears I am able to run it at the lowest available voltage across the entire frequency range:

798 MHz - 0.9250 V
1596 MHz - 0.9250 V
1862 MHz - 0.9250 V

The laptop appears to be stable at 1.86/0.9250V when testing with CPUtest and in actual usage.

Is there any reason why I shouldn't delete the two lower frequencies and force it to run the MBA at 1.86/0.9250V at all times? Will the MBA run cooler and have better battery life if I keep the 798 and 1596 frequencies in place? (In my testing, I couldn't see a difference -- it *seems* to run as cool when forced to run at 1862 as it does with the 798 setting still in place, but I can't be certain.)

Also, is 0.9250V the lowest voltage setting available to the Rev B -- is there any way to test the MBA at a lower voltage than CoolBook allows me to?

(Apologies for creating yet another thread about CoolBook, but I searched the web and this forum thoroughly and couldn't find anything regarding my specific questions. I also saw that many people who've posted their CoolBook settings kept the lowest frequency/lowest voltage pairing even though it was able to run with a higher frequency at the same voltage level.)



ayeying
Jan 7, 2010, 12:15 PM
That is the lowest voltage, you cannot go any lower.

You can delete it if you want but if the system's stressed heavily, the processor won't be able to downclock and you'll damage the CPU.

Esopus
Jan 7, 2010, 12:24 PM
That is the lowest voltage, you cannot go any lower.

You can delete it if you want but if the system's stressed heavily, the processor won't be able to downclock and you'll damage the CPU.

Thanks -- that definitely seems like a good reason to keep the lower frequencies in place, so it looks like I'll be adding them back. Wouldn't the MBA automatically shut down, though, if the CPU got too hot and there was a risk of damage?

ayeying
Jan 7, 2010, 12:39 PM
Thanks -- that definitely seems like a good reason to keep the lower frequencies in place, so it looks like I'll be adding them back. Wouldn't the MBA automatically shut down, though, if the CPU got too hot and there was a risk of damage?

The CPU diode, when it reaches that temperature will shut down. However, the diode is just one little piece on the board. You got RAM chips located and in contact with the heatsink that shouldn't go over 55 deg C or they risk damage. The resistors all over the board also have a temperature range. So the CPU may be saved, you still have other pieces to worry about.

I personally don't see the use of Coolbook anymore. The system automatically downclocks when it heats up, coolbook or no coolbook. The system heatsink itself cannot maintain the amount of heat generated for long periods of time.

Esopus
Jan 7, 2010, 01:18 PM
The CPU diode, when it reaches that temperature will shut down. However, the diode is just one little piece on the board. You got RAM chips located and in contact with the heatsink that shouldn't go over 55 deg C or they risk damage. The resistors all over the board also have a temperature range. So the CPU may be saved, you still have other pieces to worry about.

Thanks, you've definitely convinced me to keep the lower frequencies in place!

I personally don't see the use of Coolbook anymore. The system automatically downclocks when it heats up, coolbook or no coolbook. The system heatsink itself cannot maintain the amount of heat generated for long periods of time.

The MBA runs noticeably cooler now -- with the fan kicking in later -- for most of the stuff my mom does with it, so I'm happy with CoolBook for this reason alone (particularly when it's a hot Australian summer here). Of course, when she's really pushing the MBA, CoolBook isn't going to help much -- it's still going to get HOT regardless. :)

Next up, I'm going to try reapplying the thermal paste to *hopefully* get the temps down a few more degrees C.

jrabbit
Jan 7, 2010, 03:12 PM
Heat and battery life is another reason to keep lower frequencies in place.

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).

So using lower frequencies reduces heat generation, and uses less power. The system obviously has no trouble kicking up the frequency (and heat) when needed (Flash, *cough*), but letting the system relax and cool at a lower frequency when it can will use less power and let everything cool down--which give it more thermal room when it needs it next...

nph
Jan 7, 2010, 08:51 PM
Let us know how the new thermal paste turns out.