Catching up with my upgrades. Have a few PSU questions

[Gemini1706]

1- I see lots of talk about 20 pin, and 24 pin, and adaptors. This was not there a couple of years ago. What happened? Is it needed for SLI or something?

2- Dual rail 12V? Are those a bad thing? Some posts make me feel it is REQUIRED for SLI, or maybe I mis-understood?
Is it better to have Dual 12V rails or Single?

3- I never read recent posts talk about QUITEST PSU (ok, maybe not the MOST quite, but at least quite enough). What is one of the quitests PSU around that can run a high end gaming machine (500W or so)?
PC Power and Cooling used to have a good reputation for quiteness, but looks like I hear a lot of complains from people about they are LOUD.

What is a good quite PSU? Mabye in the $100 range?

Thanks a lot in advance.

[woodchuck69]

I believe the Fortron Blue Storm is calling you:

http://www.ewiz.com/detail.php?name=PS-FS500A

Sometimes you can find the Seasonic S12 500W for $100 before shipping... I don't see any currently.

[Gemini1706]

Thanks. Will look into that.
How about this 24pin 20pin thingy? What is this all about? SLI?

[Gemini1706]

wusup? no body wanna answer? :(

[Oklahoma Wolf]

Most new mainboards have migrated to the ATX 2.0 specification, which includes a 24 pin ATX connector derived from the old EPS server specification. The only difference is the -5v line was dropped. Dual 12v rails were also added to the new spec, one for the CPU and the other for video cards and everything else needing 12v.

The needs of SLI include a very strong 12v rail on both sides depending on which cards are used and how much overclocking is desired. Because SLI on the most demanding cards can take so much 12v power however, many dual 12v units give up too soon. So, I've been recommending EPS and older ATX 1.3 units with a lot of power on a single 12v rail to drive such rigs - that way, there's less chance of the PSU running out of gas before one of the two 12v rails is maxed out.

IMO, it's better to have a strong single 12v rail (32A or more) for SLI, but there are dual 12v units out there that can handle it. The Fortron AX500-A recommended earlier can power 6600GT's in SLI, but that's about the limit of it. It could probably run more powerful cards in SLI, but overclocking would probably suffer.

[Gemini1706]

Thanks a lot. That is very helpful :)