Upgrading to Crossfire Soon

[DannibusX]

I am planning on upgrading to a Crossfire set up in the coming months, and I have combed through some threads looking for specifics. I have found a lot of good information, but I have a few questions.

PSU wise, I don’t think my current OCZ GXS 700W is going to be enough to power two 5870’s, so I was looking through panchoman’s PSU Guide. It hasn’t been updated since 2007, so I want to check if it’s still correct.

The thread says that an optimal PSU for Crossfire will provide 40 Amps on a single 12v Rail. Is this still true for the current generation of cards? Some of the PSU’s I’ve looked at provide 70 Amps on the rail. Is this the new norm? Is there such a thing as over-amping a component? I don’t want to fry anything, but I do want to make sure I put enough gas in the tank for the trip.

I’m looking at buying a Thermaltake, Corsair or OCZ PSU that is modular, or semi-modular that will put out enough amps on a single rail in the 850+ Watt range. I don’t plan on running a whole lot of stuff beyond 2 hard drives, my CPU, 2 5870’s and 4 GB (2x2) of DDR3.

Sorry for my lack of knowledge in this area, but I would like to save frustration and money by not buying the wrong PSU for this upgrade and accidentally cooking some of my hardware.

Thanks in advance.

Edit: Also, if I were to Crossfire my 5870 with a 5850 would I be shooting myself in the foot performance wise?

 

[dark2099]

I would suggest posting links to the PSU's you were looking at, best way to find the one that fits you best. As for your question on over-amping a component, the rail will provide that amount of amperage, but the component will only draw what it needs. In crossfiring a 5870 and 5850 you wouldn't be shooting yourself in the foot due to each having similar/same GPU and similar/same RAM where as with the 4870 and 4850 there was a difference in RAM, GDDR5 and GDDR3 which worked, but probably not as smoothly as the 5xx0 series.