PCIe 4.0 won't actually deliver 300 watts from the slot
 

A few days ago, we reported on a story from Tom's Hardware about the power on offer from PCI Express 4.0 expansion slots. Tom's had been in touch with PCI-SIG, the governing body of the standard, and the site reported that PCI Express 4.0 would not only double the throughput of PCIe 3.0, but that it would also allow expansion cards to draw "a minimum of 300W" from the motherboard.

As it happens, the data on PCIe 4.0's upgraded bandwidth was accurate, but apparently someone at PCI-SIG gave Tom's incorrect information regarding the power provisions in the new standard. Currently, PCI Express 3.0 cards may draw 75W from the expansion slot, and an additional 225W from auxiliary ...

http://techreport.com/news/30574/pci...-from-the-slot