Would the Active Power M668 850w power supply be ok for a crossfire system? (2x 4850 or maybe 2x 4870)

Thanks in advance

At only £33.00 or so I would have to say definately no!

There is no real information available on the internet but at that price it has to be a low budget mass produced power supply of poor quality.

Go for one of the mainstream brands like OCZ, Corsair, Thermaltake, etc. I know they cost more but you can at least rest assured they will be trouble free, reliable and most of all safe.

Have a look at the Recommended Power Supply List.

Power wise 850W is fine, perhaps a little more than you need. A good quality 750W would do the job nicely.

The name alone sounds scary

Like Paul said, get a good brand name PSU, even a good 600W would be enough (Corsair HX620 comes to mind..)

Ditto and Ditto.

Do Not, and I repeat, please Do Not skimp on the power supply, especially since you are contemplating Crossfire. Paul was our resident PSU expert over at DIY-Street and he has outstanding knowledge in that area.

You've been given some good advice. Please heed that advice and save yourself some grief and possible heartache.

These are both fine, probably overkill:

http://www.pcpower.com/power-supply/silencer-610-eps12v.html

http://www.corsairmemory.com/products/hx.aspx (The 620)

liamstears

The 4870 requires 2 x 6 Pin PCI-E power connectors so you will need 4 if you crossfire. Make sure the power supply you choose as the necessary connectors.

Regards

Paul

I agree.

It never ceases to amaze me. I've been around the DIY scene for many years now, and the one constant is well intending builders who spend hundreds or thousands of dollars on high end components and then try to skimp on their power supplies. Now, so I don't come off sounding too preachy . . . . I used to be one of those folks several years ago, until a poop power supply ruined my favorite video card and a very good motherboard. It was one of those "hey here are some instructions for turning my 20-pin elcheapo power supply into a 24-pin power supply - sounds great - works for everyone" kind of things. Yep, it worked just fine for about two weeks. Then I paid for it in the end

After that I actually started taking the advice of the experts. Never again would I skimp on the power supply . . . . Ever

That is simply the best advice I can give to anyone around here. Find somewhere else to shave the bill - but not on the power supply.

Yep, I was lucky in that I only lost the 300W generic PSU I was using in a rig back in 2001 or so... since then it's been at least decent brand, and more recently, the best quality I can find

If you can learn this lesson by people telling you, rather than having to find out by stuff blowing up, you are lucky IMO lol

Well it seems like veryone has been telling you the same thing so i will just recommend a couple power supplies that i think are great for a dual card set up.

If you want top quality look at these:
SeaSonic M12 700W (one of the best power supplies out there, a bit pricey though) - http://www.newegg.com/Product/Product.aspx...N82E16817151031

ENERMAX Galaxy 850W (Pricey might be a bit overkill, but is of great quality, pleanty of connectors, amazing input and output delivery and truley high end)- http://www.newegg.com/Product/Product.aspx...N82E16817194020

Antec Quattro 850W (Kind of a contest between this and the ENERMAX i fin the Enermax to be better but costs more, i doubt you will see a difference unless your really picky about power supplies like i am ) - http://www.newegg.com/Product/Product.aspx...N82E16817371009

Great power supplies and a great price:
Corsair TX750W (Great power supply at such a low cost as, as a matter of fact most of Corsairs power supplies are dirt cheap and even cheaper with the MIR, wonder what corsair was thinking )- http://www.newegg.com/Product/Product.aspx...N82E16817139006

PC:Power and Cooling 750W silencer (Act now its on sale!) - http://www.newegg.com/Product/Product.aspx...N82E16817341011

Those are all great supplies...but he doesn't need anything more than a good 600 watt power supply (and even that would be more than enough).

true but it would be hard to find a decent power supply rated at 600W or in that range with 4 6pin connectors seeing as he wants to crossfire two 4870's....im sure ther are some but im to lazy to look at the moment
i say he should go with the Corsair TX750W not becuase it has a lot of watts but the price is amazing.