USB 3.0 Card Power?

[JaZoN_XD]

So I've been looking to buy a USB 3.0 PCI-E Card for an aging system which does not natively support USB 3.0 (Core 2 Duo). However, all of the cards I see uses some sort of external plug/cable for power, for example, either STAT power or Molex power. This got me thinking, why do these card need the extra power when they are just powering up 2 or 3 USB devices? How is the PCI-E power not enough when PCI-E power alone can handle my 60W graphics card?

[MDPS]

PCI-e isn't meant for power transportation. That's what the 6-8pin PSU connectors are for for your GPU. PCI-e was designed to transport data from your CPU's cache to the item, and vice-versa. Also, USB 3.0 draws power, so it would need a bit extra even if PCI-e did conduct. USB isn't just a data connector y'know.

[iamdarkyoshi]

its probably there if you want extra stability. why does my MOTHERBOARD have a MOLEX connector on it? Why does my old soundcard (and firewire card) have a floppy drive power header on it? Its most likely not required.

[iamdarkyoshi]

PCI-e isn't meant for power transportation. That's what the 6-8pin PSU connectors are for for your GPU. PCI-e was designed to transport data from your CPU's cache to the item, and vice-versa. Also, USB 3.0 draws power, so it would need a bit extra even if PCI-e did conduct. USB isn't just a data connector y'know.

The point made by OP is that if the slot can power a 60w GPU without any extra cables, why not a USB port or two?

[MDPS]

The point made by OP is that if the slot can power a 60w GPU without any extra cables, why not a USB port or two?

Probably because USB devices have a wide range of wattage consumption per device and the manufacturer of the card doesn't know if its for a super extreme power-hungry USB fan (just a theoretical situation as USB fans don't need too much power) or a simple thumb drive that you'll be using the card for and want to plan ahead.

   I mean, look at it from another perspective where they DON'T include that extra power connector. You have a USB item you can't power and don't have any other way of powering it other than on PCI-e, so you can't use it. It really is just forward thinking on their end.

[iamdarkyoshi]

Probably because USB devices have a wide range of wattage consumption per device and the manufacturer of the card doesn't know if its for a super extreme power-hungry USB fan (just a theoretical situation as USB fans don't need too much power) or a simple thumb drive that you'll be using the card for and want to plan ahead.

   I mean, look at it from another perspective where they DON'T include that extra power connector. You have a USB item you can't power and don't have any other way of powering it other than on PCI-e. So you can't use it.

Although USB 2.0 ports only had 2.5w, USB 3.0 still only is rated for a maximum 4.5w. It would take LOTS of USB ports to make a card need more than 60 watts of power delivery.

[JaZoN_XD]

Although USB 2.0 ports only had 2.5w, USB 3.0 still only is rated for a maximum 4.5w. It would take LOTS of USB ports to make a card need more than 60 watts of power delivery.

Alright, so basically, I'm going to get the card and try it with and without the "recommended" molex power and see if it works. I mainly want to use it for an external Seagate harddrive and that drive already has it's own AC adapter type of power supply. The USB 3.0 will only be for transferring the data.

[iamdarkyoshi]

Alright, so basically, I'm going to get the card and try it with and without the "recommended" molex power and see if it works. I mainly want to use it for an external Seagate harddrive and that drive already has it's own AC adapter type of power supply. The USB 3.0 will only be for transferring the data.

It should be completely fine. From an engineering standpoint, the only advantage that I see is that it gets its 5v rail directly from the supply rather than going through the motherboard. But if the board cant supply a clean 5v rail, its too crappy to even need a usb 3.0 card anyway lol