Did anyone notice on the picture of the melted cables that the ones on the top right where a thinner gauge than ones on the bottom.
How thick your wire is (gauge) determines it's the melting point / max load. It should be written on the cable.
The ones with "PSU" look very odd having two different gages and three wire on the top and four on the bottom.
Maybe it's a safety feature to stop it melting into a short, or maybe the manufacturer was cutting corners, I dunno, but the thinest wires are determine the max load on this cable and it's not as good as the cable on the far right with nothing written on it where both the top and bottom wires are the same gauge.
http://en.wikipedia.org/wiki/American_wire_gaugeThe pictures is what's throwing you off. The cable itself is rated at 18 ga @ 90C. There's a lot mentioned in this thread that people don't understand so let me clear some things up. XFX (seasonic design) in there 850w psu line uses an 8 pin plug that plugs into the psu. They only utilize 7 pins of the 8 pin connector, but use 8 wires. The reason for this is a 6 pin and 8 pin PCI express connectors each only use 3 hot wires while the rest are all grounds. So according to pci express specifications, a 6 pin (3 power, 3 grounds) is rated for 75 watts while an 8 pin (3 power, 5 grounds) is rated for 150w watts. So this psu design is based off pci express spec should be able to push 300w through this cable with overhead. If the bitfury unit utilizes all 3 power inputs then you should be fine. Otherwise no matter what psu pushing 300+ possible watts through three 12v power lines is pushing 9 amps through 18 gauge wire and is not a good practice. The 18 ga wire should be fine to push that amperage, but the quality of terminals/connectors whether in the psu or on the wire may not be able to support this.
If the bitfury m board doesn't have the space to accommodate an extra 6 pin power, then it would have been smart to utilize the screw attachment for a 3rd set of power connectors. Oh also you can see the one psu cable melted, but the other cable was on the verge of melting too as the cable is extremely stiff and upon trying to remove the psu cable I eneded up cracking the connector as so much heat was generated it looks to have started melting and was partly fuzed.
PSU Review
http://www.legitreviews.com/xfx-pro-series-850w-black-edition-psu-review_2239/8http://www.hardwaresecrets.com/article/XFX-PRO-850-W-Black-Edition-Full-Modular-Power-Supply-Review/1716/13