Having built a 6850 Crossfire system back in April, I've never had the system at it's full potential. I have negative scaling on EVERYTHING. I'd tried everything, overclocking the processor to eliminate a bottleneck, checking my graphics cards, checking my PCI E slots, completely uninstalling everything to do with AMD and reinstalling the latest drivers and CAP.
I never thought the problem would be my power supply because it claims that it's 650W, plenty. To add to that, my Dad said it was a brilliant PSU. How wrong he was. It doesn't even produce 450W of power. It's a coolermaster RP-650-PCAP. I have now found out the hard way that this power supply is a lump of steaming donkey poop.
So now I'm on the hunt for a power supply that will feed my system enough juice. I'm in the UK and have the budget of up to £60, I could push to £70 at a squeeze. I want as good quality as I can afford
CPU - AMD Phenom X2 550BE UNLOCKED to 4 cores running @ 3.5GHZ
RAM - Kingston HyperX Blu 1333MHz, 2x2GB
Motherboard - ASRock M3A770DE
Graphics - 2x Gigabyte HD6850s
HDD - WD 500GB Green
For a system running with two Radeon HD 6850 graphics cards in 2-way CrossFireX mode a power supply with a combined +12 Volt continuous current rating of 35 Amps or greater and with at least two 6-pin PCI Express supplementary power connectors is recommended.
Look for the Antec 520W Neo Eco Modular PSU 80Plus Bronze for £42.52 Ex VAT (£51.02 Inc VAT). It doesn't include an AC power cord so you'll have to provide your own (i.e. reuse the one from the old power supply unit). It has a combined +12 Volt continuous current rating of 40 Amps and has two PCI Express supplementary power connectors.
If you want a little more reserve capacity you can look for the Antec Neo Eco 620W Modular Power Supply for £54.95 Ex VAT (£65.94 Inc VAT). You'll have to provide your own AC power cord for this one too. It has a combined +12 Volt continuous current rating of 48 Amps and has two PCI Express supplementary power connectors.
Thanks for the replies. I had a thread on the GPU section of the site. Although I'll not get full performance with 16/4 crossfire I found out that I should still get some form of increase over one card. Which I don't.
Thanks for the suggestions, I'll be sure to check out the PSUs