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Overheating Cpu


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#1 Leonar

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Posted 05 January 2009 - 09:10 PM

"ARM® Cortex™-A8 600Mhz+ CPU running Linux"
What is the risk of overheating the CPU at full load?
And also what if someone o/c the CPU?
Did someone put all pandora in case and give sth to do (for ex. encryption) that should use all power of CPU...biggrin.gif

I know this is a stupid question.

#2 Laurent

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Posted 05 January 2009 - 09:18 PM

QUOTE(Leonar @ Jan 5 2009, 10:10 PM) View Post

"ARM® Cortex™-A8 600Mhz+ CPU running Linux"
What is the risk of overheating the CPU at full load?
And also what if someone o/c the CPU?
Did someone put all pandora in case and give sth to do (for ex. encryption) that should use all power of CPU...biggrin.gif

I know this is a stupid question.

This is certainly not a stupid question. Some people have been overclocking their chip to 900 MHz and I don't think this should be done within a case (as far as I know they did that on EVM or some other board). BTW encryption is not the best way to load the chip: one should use integer instructions, loads and stores, NEON unit, DSP and 3D chip all at the same time; running an emulator, as they exist now, is certainly not enough smile.gif

#3 Yigguth

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Posted 05 January 2009 - 09:25 PM

ARM runs very cool, there is next to no risk of it overheating

#4 Kimundi

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Posted 05 January 2009 - 09:35 PM

Yeah, it was stated several times that the cpu would becomes unstable and crashes because of a to high clockrate long before any damage would occur.

#5 Leonar

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Posted 05 January 2009 - 09:38 PM

Man but it IS over 600MHz... like Laurent wrote some ppl o/c it to 900MHz... It isn't a small frequency...

I'm not sure about safe of temperature... In case it is more hotter because it has closed air circulation.
But i hope that it will work ok biggrin.gif
The main problem is not the damage to CPU but unstable work..

Edited by Leonar, 05 January 2009 - 09:39 PM.


#6 mali

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Posted 05 January 2009 - 09:43 PM

NEON might crash it while overclocking. Also Beagle Board guys advise against it. We'll see, maybe we can prove them wrong smile.gif

#7 Phawx

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Posted 05 January 2009 - 09:43 PM

I don't think it even has a heatsink over the SoC, does it? ARM is very efficient. And by Efficient I mean less energy is released as HEAT.

Hell you can overclock Intel Atom's by 30% and those are passively cooled as well.

I doubt it gets hot enough to even burn your finger.

#8 Chip

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Posted 05 January 2009 - 09:46 PM

Unless you start messing with the core voltage, there is zero risk of overheating damage. The A8 does not have a factory set clock speed. It is designed to work at any frequency up to and including 900MHz. Just because we will be setting the default clock to 600MHz does not mean that 900MHz is "overclocked". It is still within design specs.

#9 adamorjames

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Posted 05 January 2009 - 10:23 PM

Ahh so 900 is still in the specs... that means overclocking would be.. OVER 900!

Edited by adamorjames, 05 January 2009 - 10:23 PM.


#10 Squidge

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Posted 05 January 2009 - 10:30 PM

Chip speaks the truth, overclocking doesn't cause much heat at all (and none if the core is overclocked but doing no work), its the core voltage that causes heat.

You CAN adjust the core voltage within software, but for safety reasons only safe (within specification) values are allowed. For the clock frequency, the maximum is currently unspecified, but if you go too high, the core will simply crash and require a reset - No permanent damage will be done to the core. It's upto you to be sensible here however, if you have unsaved work for example, then this could be lost.

#11 jdh2550

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Posted 05 January 2009 - 10:51 PM

QUOTE(Chip @ Jan 5 2009, 05:46 PM) View Post

The A8 does not have a factory set clock speed. It is designed to work at any frequency up to and including 900MHz. Just because we will be setting the default clock to 600MHz does not mean that 900MHz is "overclocked". It is still within design specs.

So I'm curious, why did you choose 600MHz?

#12 Racemaniac

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Posted 05 January 2009 - 10:55 PM

also try to look at this from a physical point of view
a processor doesn't generate heat out of nothing (that would be an awesome source of energy then tongue.gif), it's the power that you put in it, that becomes heat (since there's little else that can be done with it)
since these arm processors use very little power, they logically also produce less heat smile.gif

#13 Squidge

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Posted 05 January 2009 - 11:07 PM

QUOTE(jdh2550 @ Jan 5 2009, 10:51 PM) View Post

So I'm curious, why did you choose 600MHz?
The higher you clock, the higher the voltage requirements. The higher the voltage requirements, the more heat that is generated, the more strain on the other parts of the system (including battery) and the less time the SoC lives for. (decreases from 100,000 hours (>10years) to 50,000 hours (>5 years) if running at max voltage (OPP5))

To get 600Mhz requires a low voltage; to obtain 900Mhz requires a higher voltage, so it makes sense to use a lower clock and thus lower voltage.

Also, the current speed plays everything so far with plenty of horsepower to spare, so why increase it? That can be done when there is more demanding applications.

(Actually, i think it's 550Mhz at the moment on all the Pandora MK2s)

#14 Crunchwrap

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Posted 05 January 2009 - 11:14 PM

If it needs to be clocked higher for a more demanding game/application, would the software do it for you or would you need to manually increase it?

#15 Squidge

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Posted 05 January 2009 - 11:21 PM

QUOTE(Username @ Jan 5 2009, 11:14 PM) View Post

If it needs to be clocked higher for a more demanding game/application, would the software do it for you or would you need to manually increase it?
You would set a new maximum, and that maximum would be used if required. It doesn't happen automatically as you may prefer longer battery life than better performance.