Overheating Cpu

[Leonar]

"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...

I know this is a stupid question.

 

[ldesnogu]

"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...

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

 

[Yigguth]

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

 

[Kimundi]

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.

 

[Leonar]

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
The main problem is not the damage to CPU but unstable work..

 

[mali]

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

 

[Phawx]

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.

 

[Chip]

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.

 

[adamorjames]

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

 

[Squidge]

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.

 

[jdh2550]

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?

 

[Racemaniac]

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 ), 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

 

[Squidge]

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)

 

[Username]

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?

 

[Squidge]

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.

 

[CandidStan]

"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...

I know this is a stupid question.

If you're so worried about it then:

 

[ldesnogu]

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

Well at 500 MHz my OMAP3 chip is already hot, and it's sitting on a board in open air not in a box. And that's idle, running x11, so no NEON, no 3d, no DSP.

I am not claiming that increasing voltage to reach 900 MHz will damage anything, I am just not sure it will be stable, and I am in a crusade against lazy dev's that will say "crank up the clock to play my game" instead of working harder

 

[Leonar]

Yea....
@CandidStan, You can put it in your a....
But it's good to hear that there's no big risk of overheating the pandora's CPU.
Have pandora on PCB the "thermometer" on the cpu?

 

[Kramy]

Don't these CPUs consume well under a watt? I'd say the risk of overheating is zero. The risk of hitting a mhz wall due to not enough voltage is quite high.

If we're lucky, theses things will overclock past 1ghz.

 

[Nilsiboy]

I found two posts by Chip from a while ago that should settle this:

I know I've mentioned this in several other threads, but here it goes again: Heat is not an issue.
You may notice that the Pandora itself does not have active or passive cooling. It doesn't even have ventilation holes in the case. The SoC does not get hot.

It's been a long time since I've been in a physics classroom, but lets do some really bad science.

Joules = watts x time in sec.

Temp rise = joules / mass in grams / specific heat of mass

If we assume the Pandora has a mass of 300g (slightly more than the original DS), and the SoC is responsible for .25W of heat load (the maximum TDP), and the average specific heat of the device is 1 (this is WAY too hard to calculate accurately. It's probably between 1 and 3), then an OMAP 3530 SoC running balls out for 1 hour could theoretically account for a maximum system temperature rise of about 3C. And that assumes that absolutely no heat escapes from the system through conduction. It assumes about a thousand other things too, but you get the idea.

I know this isn't anywhere near accurate, but it paints a pretty good picture of the sort of temperatures we're dealing with. The heat generated by the SoC is minimal. The heat generated by the other components is minimal. You could entomb your Pandora in three feet of neoprene and it still won't overheat.

and the SoC is responsible for .25W of heat load (the maximum TDP)

Where did you get that number from? That seems very low for a 600 MHz Cortex-A8 + 430 MHz c64x+ + 1xx MHz SGX + 128 MB LP DDR @166 MHz...

Damn. I know I remember seeing .25W TDP somewhere. Turns out it was for the Cortex A9. I can't find a straight up TDP rating for the 3530 anywhere, but ARM claims 0.59mW/MHz for the A8 which gives you about .35W TDP @ 600MHz for the CPU alone. I've no idea what the other parts contribute to the thermal load but even if you double the CPU rating and assume .7W for the whole thing (that's probably on the high side) you still only have less than a 9C temp rise under the worst case scenario.