help wanted: what is the purpose of optional block? about pi5_pcie

[mfolejewski]

that's SUSCLK (32kHz)

"SUSCLK is a 32 kHz clock useful for card power-saving but not required in practice"

https://hackaday.com/2022/11/03/m-2-for-hackers-connectors/

[m1geo]

Correct. It is to allow peripheral devices to operate from a slow, low power clock in order to do things like assert PCIE_WAKE#. Useful for things like wake-on-LAN.

The FPC connector is able to supply 1A (500mA per pin) at 5V. This is enough for some PCIe/NVMe devices, but not all. If you need more current, the additional power from the GPIO pins may be helpful. They appear to be connected together based on a simple DC resistance check.