Hi, I bought this Antec Earthwatts 750 power supply and I want to know, what is the max amp on the +12V that I can use for graphics card? Do I just add them together or it is not that simple? It totals to 100 but I don't think it is that high. Can it support a 5870, 6870 or GTX470? When it is stated that "500 Watt or greater power supply with two 75W 6-pin PCI Express power connectors recommended" for a 6870, how can I tell the wattage coming out of the PCI-e connector?
You don't need to worry about the PSU.. It can easily power any single video card available in the market and many dual video card setups also.. Now, since its a 750W PSU, logically the max amps on the +12V rail can be 60 (12 x 60 = 720).. However it adds upto 100 in the mentioned specs which is a bit confusing.. Surely some expert will eventually see this thread and clear the confusion for both of us..
The difference is in what a single rail can handle vs what the single source feeding all those rails can actually output. Meaning that while each rail has the wiring and ability to handle 18A or 20A, the 12V source feeding them can't provide max power to all rails at the same time. If inside the PSU your transformers can only output 60A, it doesn't matter if you have 5 rails rated at 20A each. You can only output 60A.
This might be a surprise for some, but nearly all multi rail PSUs on the market now are really single rail. The PSU takes in AC power, converts it to DC, and then uses current limiters to form the rails. Each rail does NOT have its own transformer, etc.