Re: Clarifications about PPS SHM content

[Martin Boissonneault]

Hi!

I ran a test with ntpheat for a day, and my jitter StdDev jumped from 
~275ns to ~700ns. For my setup, it's NOT better.

I'll see if my physical "mod" will help: I stuck two layers of sticky 
thermal pads on top of each other, covering both the CPU footprint and 
the crystal, on the underside of the CPU. My idea is to better conduct 
heat from the CPU to the crystal while reducing heat transfer transfer 
to air. The pads have better thermal conductivity than air, but being on 
top of components like a blanket should provide some isolation to air. 
Heat should spread a bit better between nearby components and the PCB, 
but I have nothing on top to wick heat away. If I had thicker pads (mine 
are pretty thin), I'd try to put a piece of metal to spread heat across 
the whole area.

My CPU usage is already 25%x4 cores, there is some heat there. I just 
have to stabilize it across the xtal and prevent too much air movement.

I will report back later!

Martin

On 2020-03-27 06:03, David J Taylor wrote:
> Either way, in ascending order of stability - all other things being 
> equal
> -  I would say:
>
> freewheeling temps - lowest
> ntpheat - better
> insulated environment - best
>
> Paul Theodoropoulos
> www.anastrophe.com
> ==========================================
>
> Paul,
>
> I'd agree with that order of performance, although my "insulated" is 
> sitting in a walk-in cupboard on an outside wall, normally closed all 
> day and night - little diurnal delta T!
>
> I wrote up some basic notes here:
>
>  https://www.satsignal.eu/ntp/Raspberry-Pi-ntpheat.html
>
> Using the GPU would be nice, although not needed in my application.   
> I added a link to Folkert van Heusden's program to heat the GPU.
>
> Cheers,
> David