lemming9 :
Would like some confirmation on these points:
1. Does a 2 molex to 8-pin PCIe connection provide the full 150W/12.5A just like a standard 8-pin PCIe connection would?
2. Also, are the GPU, CPU, molex/sata drives, MB all powered from the +12V rail?
3. If so, what do the +5V +3.3V -12V +5VSB power? The fans, USB ports and RAM?
Thanks
1. No it does not. Each Molex connection is rated at 40 watts. 6 pin PCIe are rated at 75 watts. 8 pin PCIe are rated at 150 watts. A 2x Molex to 6 Pin PCIe is safeish as it provides 80 watts (meaning that it should work, but a PSU that is deficient in PCIe connectors may not be up to the task), but a 2x Molex to 8 Pin PCIe is not. There's a real fire hazard there.
2. The CPU, IGP (if present), GPU, memory, and chipset are all powered through programmable voltage regulators. These take in 12 volts and spit out a programmable value, typically in the 0.5 to 2.0 volt range.
Fans and pumps use straight 12 volts, USB and other powered connectors use 5 volts. Peripherals such as hard disk drives and optical drives typically use a combination of 5 volt and 3.3 volt supplies.
The motherboard uses an assortment of voltage levels for varying components. Many integrated circuits still use the 3.3 volt LVCMOS standard. LEDs and other bells and whistles may use either 3.3 volts or 5 volts depending on design.