IFC-PCIE2U3 4-Pin Power Connector

[dieu]

What is the purpose of connecting the 4-pin power connector of the IFC-PCIE2U3? I currently have the IFC-PCIE2U3 installed in a PCIEX16 slot and see no performance loss by not having the 4-pin power source connected. Currently, transfer rates are approximately 90 MB/sec. Is the 4-pin connector only required if the slot is not a PCIEX16, i.e., PCIEX4?

[drmemory]

USB 3.0 can draw more power than the PCIE bus specification, so you need this connector to supplement power to the card, from the power supply.

[dieu]

Thank you for your response. To clarify, I installed the USB 3.0 PCIe card into an Asus P6T PCIe 2.0 x16 slot. As my transfer speed was 90 MB/sec, what risks are there if I do not supplement the card?  I have used the card both ways and have not experienced any difference in performance and or issues. 

[drmemory]

When you connect two devices, you may see a Current/power draw that the PCIE slot is not capable of supplying. The devices may not be recognized properly, or only one may be recognized. Worst case, is that the PCIE card will try to draw too much current from the motherboard and overheat or damage a circuit.

Then again, your motherboard may supply enough Current for the card - it's just that the PCIE spec (connector) doesn't comply with the required Current draw of USB3.0