How does multiple 12V rails work

[rstove02]

Currently using a S12 seasonic 500 watt power supply that has two 12V rails a 16A one and a 17A one.

How do I know which power connectors come from which rail....there are like 8 cables coming out of it....SATA power cables, 4pin power cables, 6pin power cable (for video card)...etc..etc...?

Just upgraded from a 7800GT to a 8800GTS and having some intermittent problems (DVD drive not being detected by BIOS, X-fi sound card not producing sound even though it exists in hardware manager) and was wondering if I am overloading one of the 2 rails and how to go about rebalancing the load on them.

 

[idiotekniQues]

from what i have read, it may say 2 or 3 rails but its really 1 big 12v rail.

for the corsair 620ex, made by seasonic, this is said to be fact as per johnny guru

 

[jonnyGURU]

http://www.jonnyguru.com/forums/showthread.php?t=1036

Read "Watts don't mean squat" and "Why do they split up 12V rails"

The Corasir really is only one +12V rail, as are other Seasonics that claim to have three or more +12V rails.

The S12-500 really is two +12V rails.

What connectors go to what rail? Easy. As per ATX12V spec, ALL connectors get their +12V from one rail. The other rail is ONLY for the CPU (via 4-pin ATX12V and/or 8-pin EPS12V connector.)

 

[rstove02]

Thanks all for the replies.

Here are some more questions for johnnyGURU:

My 1.5 year old Seasonic S12-500 power supply has the following stats.
+3.3V@30A, +5V@30A, +12V1@17A, +12V2@16A, -12V@0.8A, +5VSB@2A

Would upgrading to a newer model Seasonic SS550-HT with the following stats.
+3.3V@24A, +5V@30A, +12V1@18A, +12V2@18A, +12V3@18A, +12V4@18A, -12V@0.5A, +5VSB@3.0A

Would think that with the 12V rails increasing from 16/17 to 18A plus having 4 rails to distribute load of a high end PCIe video card instead of the 2 would help?

 

[jonnyGURU]

I haven't taken apart the SS550-HT myself, but I'd be willing to bet it's not really four +12V rails.

Like I said, typically the Seasonics that claim to have three or more +12V rails (the newer ones) tend to really only have one big one.