[PD] new raspberries

[Simon Wise]

On 10/02/15 06:49, Chris Clepper wrote:
> In general, the ARM will do all sorts of things to keep energy usage to the
> bare minimum:  Video decoding runs on dedicated DSP/GPU rather than the
> main cores, parts of the cores are shutdown, RAM is put to sleep and so on.
>
> Using -nosleep on a root process at elevated could defeat enough of the low
> power safeguards as that is something an Android phone/tablet would never
> do.  All of those devices have heatsinks just due to space constraints, and
> Apple ran afoul of customers due to excessive heat on a dual A8 based iPad.
>
> Without any heat treatment on top of the CPU most of the heat flows through
> the PCB.  So in some cases the issue wouldn't be with the ARM but some
> other part reaching its thermal limit (like a power regulator or RAM that
> have to be physically close to the CPU).  The UDOO board's WiFi chip gets
> hotter than the ARM heatsink for example.  Freescale recommend heat
> spreaders and sinks for all of their iMX.6 parts although not all of the
> low eval boards have them.

the Udoo I have has a very substantial heatsink, much much bigger than the older 
models, I guess this could be the reason.


Simon

>
> The Pi 2 doesn't have much thermal cooling on the chip and the RAM is
> directly UNDER the CPU so the heat from both will largely go into the same
> place PCB.  Maybe there is enough copper in the PCB to dissipate the heat,
> but the thermal docs I have from Freescale say it's not possible to do for
> a 5W+ quad A9.
>
> On Mon, Feb 9, 2015 at 1:53 PM, Miller Puckette<msp at ucsd.edu>  wrote:
>
>> Interesting.  Of course, it _should_ be thermally permitted to run all
>> cores at speed - and the Pi folk are taking heat dissipation very
>> seriously in their thinking.  So my leaning would be to risk $35 on a
>> week-long stress test using -nosleep.  Hmm, time to order a machine...