Pcie Cable Ratings ?

[mactronix]

Hi,
I like many others am fed up with the whole recomended specs thing with graphics cards and so am setting out to increase my understanding of how the power is supplied.
Can someone please tell me if the PCIE connector has to deliver 75 Watts as standard ?
I beleive the PCIE slot on the MOBO is 75 watts as standard ?
So and i realise there is a good chance it wont work like this but. If i have a dedicated PCIE cable and not one cobbled together fron a couple of Molex connectors, then does it follow that i am capable of supplying 150 Watts to any GPU ?
This sort of logic worked with the older cards that didnt use power cables, "If the card hasnt got a power cable it will run ok as the slot has to supply enough power as standard".
So does it work that way or not ? If not please could someone either direct me to a good source of info so that i can get a better understanding of it myself or possably offer a brief explanation.
Thanks
Mactronix

 

[Mousemonkey]

I'm pretty sure you are correct in your thinking sir.

 

[mactronix]

Ok so to follow on with that vein of thinking then. If i have a GPU that has a single PCIE connector like say.....oh .....A 4850 then my power supply has to be able to power it if it has said dedicated connector ?
Just to let you know this all came about when i realised that sapphire listed the same spec for power requirements for both the 3850 and the 4850. Namley a 450 watt power supply with a 75 watt pcie connector. However review sites that had conducted tests clearly show that the 4850 uses about 40 watts more than the 3850.

mactronix

 

[Mousemonkey]

Maybe it's because not all boards are capable of providing a full and steady 75 watts continuously through the Pci-e slot (regardless of requiring a molex to be plugged into the board) hence the extra dedicated feed is required to take up the 'slack', either way the card cannot use or get more than 150 watts leaving 300 for the rest of the machine.

P.S What if the 3850 needs 95watts and the 4850 needs 135watts?, both require more than 75watts but can still run on a 450w PSU but will both still require a dedicated power feed via a six pin supply.

 

[mactronix]

Well yes i guess i can see that. From the numbers i have seen a 3850 runs about 70 watts so i guess the pcie connector is like a safety net.
The 4850 needs about 110 so that means it definatly does need the cable.
Thanks for that anyway the thing is my PSU has the cables and is 460 Watt but only 26 Amps. I just got to thinking, hang on here someone is taking the pee. The PSU manufacturer is either putting connectors on that are of limited or no use or Sapphire are being generous with there safety margin. I guessed the latter but wanted some confirmation that my thinking was correct.

Thanks again
Mactronix

 

[Mousemonkey]

The recommendations given on the box are usually based on a top of the line CPU based system like a QXxxxx or some such, so as long as you don't have too many HDD's and a heavily OC'd CPU you should be OK I would have thought.

 

[mactronix]

Well i have a midrange duo and at the min 1 but i may add another optical drive, one spinpoint 500 HDD and a card reader. Hardly what i would call fully loaded.
I do realise that the whole it has the cables so it should run it thing needs to be given some safety margin,just to be sure.
Cheers
Mactronix