Time to clear up the many wrong statements that people are making in this thread. I am the person who made the first powered PCIe extender and who documented why this is necessary: http://blog.zorinaq.com/?e=44

Firstly, the current drawn through the PCIe slot vary a lot depending on the card. Dual-GPU cards usually draw more than single-GPU ones (contrary to what someone said). Here are some of my own measurements with a clamp meter around the 12V lines of a PCIe extender, while Bitcoin mining:

HD 6990: 4.2 A
HD 5970: 4.1 A
HD 5870: 3.2 A
HD 6950: 2.5 A
HD 7970: 0.9 A

So for example the 7970 (and probably most other 7xxx series cards, but I have not tested them) draws so little power that they pretty much don't need powered extenders.

Also, eroxors, most of your cards are pretty low-end/mid-end. They likely all draw less than 3 Amp or so because your most power-consuming one seems to be the HD 5870 (3.2 A through the slot). Even if you had 4 of these cards, that's only 12.8 Amp total, so only 6.4 Amp per 12V wire of your 24-pin ATX adapter.

But most importantly, whether the 24-pin ATX connector overheats or not depends a lot on whether the Molex Mini-Fit Jr. pins in the PSU 24-pin plug have a single or double spring. You can tell by removing the pin from the plastic housing and seeing if it has one or two pairs of "dots" at the end. This one has two: http://www.alliedelec.com/images/products/Small/70090646.jpg The single spring pins (typically used by inexpensive PSUs) have a higher (edit: electrical) resistance and are more prone to causing the connector to burn out over time.

For example, in my farm of 4x5970 and 3x6990 machines from the old days, I noticed that upgrading from single-spring pins to double-spring pins pretty much made powered extenders unnecessary.

Finally, eroxors, you are right that the memory subsystem of Radeon cards (at least the 5xxx I tested years ago) is powered through the slot, not through the 6-pin or 8-pin power extenders. So Litecoin miners need powered extenders more than Bitcoin miners (at least for 5xxx and 6xxx cards, again the 7xxx series seems to draw so little from the slot, that powered extenders may not be necessary).

This doesn't mean I'd lend him my BTC, but I think you guys should cut Bennet some slack. Even Tomatocage has him on the green list.

I have 4 card setups that have burned through pin 3 ATX connector on the mobo from the PSU

After 2 PSU's I use powered risers ...everything is LTC

Even when i started out i was buying old cards from forum members (noob mistake) ...they would mine BTC all day all night but would crash and burn even trying to mine scrypt

Even with 3 cards on risers and one on the board they will run for about 2-4 weeks and then cards start to disappear (i.e u will drop a card and suddenly its a 3 card rig ) you either have to bring another card back down to the board which starts to run into heat issues

So 250 GPU's is impressive ...but i think we can say we are talking about BTC only...either that or my 70 gpu farm is totally fucked in my approach

All new vtx 6970's (2 months old)
All New Sapphire 7950 vapor -x (2 weeks old)
All New MSI 990fxa gd 80 v2

I would love it if i was wrong but so far powered risers seem to be the solution ...I only got them 5 days ago and so far they have stopped cards falling off a rig and no more toasted PSU's

Intrested to hear any advice to the contrary

How many PCIe 1x do you use per board? Do you use scrypt based coins ? Do you have 5870 ?

PCIe 1x doesn't support as much power as PCIe 16x, 5870 draw power from the PCIe connector for the RAM and scrypt-based coins are RAM intensive. I have a board that ran for more than a year mining bitcoins with 5x 5870, 4 of them connected to PCIe 1x connectors. It died in two weeks mining litecoins (the 12V power lines burnt through the PCB).

I can feel the difference between sha256d and scrypt just by touching the PCB on another board of the same model. Replacing extenders with powered ones gradually decreases the temperature.

I have the same experience with 5970s: they don't seem to require as much power from the PCIe connector than the 5870s.

So powered pci-e extenders aren't largely unnecessary: the combination of motherboard model, actual cards used, opencl kernel used, ram and gpu settings makes it impossible to predict what will happen without powered extenders unless you already tried the same combination. If it worked for you without them, consider yourself lucky.

I'm interested if: not a scam, and payment accepted in ltc.

I think the people who are burning out their boards are either running many cards with *significant* overclocks/overvoltage, or these people didn't have good connections to their card(s) (which drives up resistance, thus driving up the current needed).

How many cards per rig ?

Come on, do you really think im trying to scam???

Please consider doing a 2-chip version. Downclocked to 256 mhz would be a really nice usb stick.

Can't help you as far as getting connectors, but once you get them can you keep the thread updates as to how well they work?  The reason I am curious is because I saw a thread before about those adapters and people were having troubles getting more than 1 to work.  It would be nice to see if you can get em' to work. 

I'm looking for a Referral to WGU which grants a discount on the application fee. I think that there are a few students here. Willing to pay a small tip to someone willing to help. Thanks.