The voltage regulator on a V006/008 riser is there to stabilize the line and prevent spikes, not generate 3.3V. Why would the traces of the USB connector where the 3.3V is passed from the motherboard on the V006/008 risers be connected to the pins leading to the PCI-E slot on the riser if the riser created it's own 3.3V?
https://en.wikipedia.org/wiki/PCI_ExpressPowering the riser with a different PSU as the motherboard causes the 12V line to come from one power source and the 3.3V line and the grounds on the riser x16 PCI-E slot to come from mixed power sources, which is the problem. Sorry, but anyone that says it's safe to power four risers off of one molex strand,
clearly doesn't know what they are talking about when it comes to mining.
I said those that cannot run more than two Molex connectors on the same bus without getting hot are experiencing a switching PSU phase short. I did not say I recommend it. You send me a link to a generic wiki page, as if the Chinese even bother to follow PCIE protocols when designing risers.
You sir clearly don't understand how a switching PSUs operate, nor do you understand how the riser operates. The 3.3v is generated from the 12V source. You can clearly following the tracings from the 12v source and they end up at the 3.3v regulator, coil, and capacitor circuit. If the 3.3v was not produced from the 12v then what is the coil there for??? It's clearly a 12v to 3.3v regulated circuit. Heck, the number 3.3 is clearly stamped on the regulator on v006 boards.
The 3.3v bus isn't of consequence, the 12v bus is. The 3.3v is regulated and no longer has a switched phase, therefore it's isolated from the switched PSU and doesn't get affected by the MB PSU. You are focusing on a fly and ignoring the elephant. The 12v switched riser will eventually go 180 out of phase with the GPU PSU and will fry something. You have two engineers tell you otherwise and you still argue something you CLEARLY know little about. Go ahead and burn your house down.