OLPC XO 1.5 overheating problems

[Tiago Marques]

Hi John,

On Tue, Oct 6, 2009 at 6:45 AM, John Watlington <wad at laptop.org> wrote:
>
> On Oct 3, 2009, at 12:16 PM, Tiago Marques wrote:
>
>> On Sat, Oct 3, 2009 at 4:19 PM, Ed McNierney <ed at laptop.org> wrote:
>>>
>>> Tiago -
>>>
>>> Well, everyone gets to contribute something to thermal problems :-)
>
> Actually, the average heat sources are (in descending order): the companion
> chip (graphics engine, memory interface, and peripherals), the CPU, the
> DDR2,
> the WLAN (!), and the clock generator.  At peak operation, the processor
> wins.

I see, never thought the VX855 would dissipate so much while idling,
perhaps VIA doesn't do clock gating?

>
> We are working to reduce the WLAN dissipation, and I'd love to be able to
> afford a lower power clock generator as well.
>
>>>  But the CPU's the main source and also provides internal throttling
>>> mechanisms to
>>> manage it (along with the external heatspreader mechanisms, of course).
>>
>> I hope that the heatspreaders might fit in your budget for the
>> machine. I've seen all kinds of bad happen to machines where
>> throttling was necessary.
>
> There is definitely a heat spreader.   We have encountered problems
> in the past with manufacturing problems that contributed to a less
> than stellar contact with the chips being cooled, and that appears to
> be contributing to the current concerns.

I see, nothing too uncommon, even in shipping hardware unfortunately.

>
> The throttling is a measure of last resort.  It means that if you DO operate
> an XO in a room that is a few degrees too hot, it won't crash.  It will just
> slow down.

Good to hear that! Keep up the great work.

Best regards

>
> Cheers,
> wad
>
>