World's Most Stable Raspberry Pi? 81% Better NTP with Thermal Management
24 points by taras
24 points by taras
Alternative : adjust the quarts measurements based on the surrounding temperature, e.g. https://www.sensorwatch.net/docs/watchfaces/nanosec/
Lemme see if I've got this right … dedicate three out of four cores merely as heaters for one core so it'll always run the xtal at the same frequency? That's … a mood.
I was kind of hoping for a Raspberry Pi with a great big huge OCXO hanging off it. But having mingled with some extreme hifi types who buy things like hard drives with external OCXO clocks, maybe I really don't want to see another of those ever again
In the comments where this was posted on the orange site, someone linked this stack exchange post where there's info on swapping the oscillator entirely (TCXO?)
https://raspberrypi.stackexchange.com/questions/74482/switch-out-the-x1-oscillator-on-a-rpi-2-3
A TCXO is more stable than the stock part, but it relies on a calibration curve to correct the frequency deviation. These can be very stable, and don't require the oven (and its large current draw) that holds the OCXO at a constant temperature.
DS3231 RTC chips can be calibrated against a GPS time source to give remarkably accurate results. They're not useful as a CPU clock, however
i have a rpi5 running ntpd-rs on nixos [0] and have been pretty stable (i think… at least by my standards) [1] for the past months and i didn’t do any tuning… the source uncertainty coming from pps is around 99ns which is around 2x what the author got :<
[0] https://github.com/stepbrobd/dotfiles/blob/master/hosts/server/isere/time.nix
[1] https://bsky.app/profile/stepbrobd.com/post/3m56ydcylxc2y