1000W PSU rails and 4 GPUs

[tynt]

I have this Antec TruePower Quattro 1000W, 4 x 25A rails, 840W total. This should be more than enough to power 4x HD6870 (140W each, two 6pin connectors each)?

12v1 - 12v EPS MOBO connector that power CPU and MOBO.
12v2 - modular connectors for HDD
12v3 - PCIe modular 6+2pin(y-splitted to 2 x 6pin) and 6pin
12v4 - PCIe modular 6+2pin and 6pin

Three cards was easy to connect, everything runs fine even with heavy OC.
To connect fourth card i made an 8+2pin to 6pin Y-splitter. Now I divided 4 cards to 3 rails like this:

12v2 - 3 PCIe connectors - load: 18A
12v3 - 3 PCIe connectors - load: 18A
12v4 - 2 PCIe connectors - load: 12A
I measured connector voltages, all are nicely +12.2volts (+/- 0.05v)

Four cards setup is pretty unstable, crashes every 4 hours even w/o OC. And cards OC much less than in 3 card setup.

Am I having PSU problems? And how do you guys connect your cards when there are not enough connectors?

[jrtubs]

What kind of temps are you getting if you're able to mind for a few hours it sounds more like a heat issue. Antec are nice power supplies and have a good bit of headroom like an extra 100watts if u want to push it right to the edge. but really u don't want to be pushing it that hard. as for connections your video card normally comes with extra adapters.

[legolouman]

Unless something is failing, I doubt it's a power problem. It's most likely a heat issue if you can mine for a few hours. There's a lot of heat coming out really fast. Watercooling is recommended, but you could just ditch the case

[tynt]

Problem solved. 100% CPU usage caused to rig to hang randomly. I downclocked and undervolted my CPU and set miner affinity to one core.

Now all cards are OC-d again and rig runs like a dream.

[HolodeckJizzmopper]

Out of curiosity, which tool are you using to downclock your CPU ?

[tynt]

I'm using Athlon x4 640 (3GHz default). I underclocked and undervolted it to 800MHz and 1.2v in BIOS.