Depends on the system. On newer Intel machines, it will prevent the SoC from going into lower power states than PC2. On my laptop, that means idling at 5 watts

Depends on the system. On newer Intel machines, it will prevent the SoC from going into lower power states than PC2. On my laptop, that means idling at 5 watts instead of 2ish watts. That said, I don't think any laptop has a PCIe to PCI bridge. This should only affect some desktops and servers.