[time-nuts] Raspberry Pi TCXO Hat

[MLewis]

The Pi 4 launched with issues, including heat issues, but has been 
improved. The improvements in power usage are supposed to reduce the 
heat issues. A new bootloader was released. It includes that by default, 
power will be maintained on the power pins, so power is maintained on hats.

https://github.com/raspberrypi/rpi-eeprom/blob/master/firmware/release-notes.md
https://www.raspberrypi.org/downloads/

There's a new tool for updating the Pi 4 bootloader EEPROM.
https://www.raspberrypi.org/documentation/hardware/raspberrypi/booteeprom.md
https://github.com/raspberrypi/rpi-eeprom

https://hackaday.com/2019/10/30/rpi4-now-overclocked-net-booted-and-power-sipping/

"The USB controller will get hot based on its usage now, instead of get 
hot always. If you use it to its fullest it will get just as hot, but if 
you don�t use it much or at all, it will be cooler."

"the bootloader (and associated firmware) actually reduce the power 
consumption of both the USB controller and core SoC, with the USB 
controller accounting for about half the power saving.
...
PCIe ASPM savings actually account for about half of the idle power 
savings realised so far. Throughput loss to mass storage due to ASPM 
appears to be in the ~2% range.

The rest is made up of SDRAM PHY optimisation, clocking improvements, 
changes to the load-step response of the PMIC (allowing us to reduce 
load-step margin on the core voltage). We also have a DVFS scheme which 
makes the first (1GHz) frequency back-off much more energy efficient 
than it was at launch."


Michael

On 02/11/2019 5:13 AM, David J Taylor via time-nuts wrote:
> ...
> Just perhaps with a RasPi-4 you /might/ see an improvement as the 
> Ethernet has a more direct path, but that's a board where 
> self-generated heat is greater, so the thermal issues might make 
> things worse.
>
> Try it and see!
>
> Cheers,
> David