I dont doubt what you guys are saying. Im sure in some situations the molex is a good idea. But to say its needed for any and all dual chips or more than 4 cards is complete bullshit. What should be said is they might be a good idea if your using cheap equipment or trying to run more cards than what your board was intended. If you have a decent board and psu that was designed for multiple cards you will not NEED the molex. Your equipment will run just fine without it and you will have saved yourself some money.
Ok. Here's what it boils down to.. the PCIE spec allows for up to 75watts to be pulled through a PCIE slot. Most cards only pull 25watts, with your higher end/dual gpu cards pulling the full amount. Some board manufacturers will cut corners and think "They won't use all 6 PCIE slots at one time, so we'll only account for 150 watts for that" and go cheap. Then you go and use risers to make more cards fit than what would normally and before you know it, you've got 6x25=150watts of draw. Ok, not an issue. The board the designed for 150 watts. If any of those cards starts pulling more than 25watts and the board was made cheaply, you're screwed.
See how both sides can actually be right in this situation? It really comes down to your exact mix of hardware. So you run 6x5830s. We all know different brands run their cards slightly different. One person's 6x5830 might pull more than a different person's 6x5830s. Its easier to make a blanket statement about using molex than it is to go and explain all of this, especially to n00bs.
That being said, I think 22.95 for a riser is a bit much, although I have bought some when I couldn't get them elsewhere.
Interesting direction this thread has gone... I've had 3 5970s and a 5830 going strong for about 4 months on standard extenders without issue(1200watt corsair,gigabyte ud3 mb). I never thought about overdrawing power from the pcie connector but this thread has me thinking. I'm only drawing 1000w at the wall but I can't get my system to boot with any more cards. I'm thinking I need a pcie extender with molex, and that I'm lucky I haven't burnt anything out yet.
With that said, I hesitently started to order one from cablesaurus. $22 is ridiculous, add $6 shipping on top of that and it's enough to make me change my mind. From the pics it looks like they just soldered a single pin molex connector to one of the exposed pcie pins. I may break out the old soldering gun and make a few myself. Anyone have any experience making their own?
This;
https://bitcointalksearch.org/topic/fs-custom-length-pci-e-extension-cables-with-or-without-molex-power-38725
