A 6 pin PCIe connector for a video card is rated 75 watts maximum. A 6+2 pin connector is rated 150 watts maximum. The PCIe x16 slot is rated 75 watts.
I have some Radeon HD 7990 video cards that have two 6+2 connectors. Interestingly, there were two 6+2 to 6 pin adapters included with an MSI Radeon HD 7990 that I bought new. I tried to run the video card with those adapters and the mining rig locked up repeatedly until I removed that card from service. When I looked into the 6+2 connector on the adapter, only five of the six slots had pins. The missing pin is one of the positive (not ground) pins. Unknown wattage, but presume 75 instead of 150 watts.
Lesson learned: I had bought a generic, flat, supposedly for OCZ, 6+2 cable over a year ago to use on one of the video cards. I have chased problems with that video card for the whole time since installing it. When one of my original OCZ ZX cables failed this week, I compared the original and the replacement. The replacement cable only uses six pins, not 8! The problem was that the video card was under-powered. The card must have been running on the ragged edge of power limitation. It sporadically caused the computer to lockup. I have four new cables on the way and they have eight pins in both ends.
I have some Radeon HD 7990 video cards that have two 6+2 connectors. Interestingly, there were two 6+2 to 6 pin adapters included with an MSI Radeon HD 7990 that I bought new. I tried to run the video card with those adapters and the mining rig locked up repeatedly until I removed that card from service. When I looked into the 6+2 connector on the adapter, only five of the six slots had pins. The missing pin is one of the positive (not ground) pins. Unknown wattage, but presume 75 instead of 150 watts.
Lesson learned: I had bought a generic, flat, supposedly for OCZ, 6+2 cable over a year ago to use on one of the video cards. I have chased problems with that video card for the whole time since installing it. When one of my original OCZ ZX cables failed this week, I compared the original and the replacement. The replacement cable only uses six pins, not 8! The problem was that the video card was under-powered. The card must have been running on the ragged edge of power limitation. It sporadically caused the computer to lockup. I have four new cables on the way and they have eight pins in both ends.
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