i need a power supply and i found one thats SLI ready for like 34 bucks, 575w, pretty decent.. anyway, i have a crossfire card radeon 3870 hd 512 256 bit gddr4 (which is smokin! eats every game like a champ).. so is the whole sli/crossfire ready bs just a marketing scheme or is there really a difference? i mean, both have 2 pci-e 6 pins in them, whats the difference if i hook it up to nvidia or ati card? thanks!

There is no difference. Some genius in a marketing department somewhere probably came up with labeling power supplies as SLI or Crossfire ready.
 
Same thing with "Vista Ready" monitors.

Xfire ready generally means it has 2 8 pin 12v and 2 6 pin volt cables attached to the PSU.  Same with SLI cept a total of 4 6 pin 12v cables.

I have a SLI PSU in one computer and a Crossfire PSU in a different one. The only real difference is the paint job and that the Crossfire one has a couple 8-pin plugs. One other thing, check out the tier listings for PSUs before anything is bought. Somehow I very much doubt that a good quality SLI ready PSU can be found for $35,

 
Agreed all the way
 
Also agree with Sailer be carefull
The price is very very high if you got a sh---ty PSU
Might cost you everything inside your box
Only screws might survive
   

i figured it was all bs.. what are the 8 pin connectors for?  can i still crossfire the cards with 6 pins or not?
 
thanks for the advice guys

If you are spending money on two top end video cards DON'T buy a $35 PSU!! You need to spend >$80
 
      Mike.

Usually if it has a thing saying SLI or Xfire certified it means ATI/AMD or Nvidia have tested the PSU with an SLI or Crossfire setup and concluded that it worked with stability.  The problem being, it may say SLI certified, but if you go to Nvidias or ATI's sites to look at Xfire/SLI compatible PSU's it will be certified for an older dual card setup, not usually for whats out now.  
 
But usually anything that says SLI/Xfire supported will be able to pull it.  Just need to make sure there is enough current on the 12v rail/Rails, and enough pcie connectors.  Think the 8pin pci e connectors are for the older ATI high end cards.  My 3870 only needs 1 6pin connector.

@ mike 99: i, so far, have only one card, but i want a psu to support two in case i need it
 
so its pretty much safe to say that i can get either sli or crossfire "ready" psu and it will work no problem?  
 
@ mathos: what about 12v rails and what the hell are they? i'm a total noob when it comes to power supplies.
 
edit: i just found this one for pretty decent price with 3 12v rails and its modular, should i get you think?
http://www.newegg.com/Product/Prod [...] 6817371016

 
550 W
I do not think it has rnough power to run fully equipped PC with 2 high end graphic cards

SLI/Crossfire PSU's are pretty much the something, with the required connectors available from the PSU.
A $35 575W PSU is a ripoff, and a waste of money.
A quality, efficient, capable PSU in that range will run you $100.
Hit the PSU sticky and look at the PSU charts.
   

so is the one i posted a good one or not?

The thing I noticed is that SLI/Crossfire ready just means it has 2+ power connectors (6 or/and 8 pin) for GFX cards where non SLI/Crossfire ready PSU's do not (alway's) have this.