I have recently bought a new psu called Axp 850 watt or Xion Axp 850 watt. It also says 720-900 watt on the package. I also bought a new graphic card with it. The Powercolor 4870x2, but it don't work? It's quite new and I know the card is working it selfs. Can the psu be the problem? My system doesn't use 850 or even 720 watt at full load. Some other guys said that I should had bought the Corsair 650 w instead?
Make sure the 4/8 pin connector is plugged into the mobo and the 6-pin PCI-E plugs into the Video card.
If you work thru the info. below you should be able to determine what the issue is.
As far as PSUs are concerned, be informed. Before you buy any PSU read accurate, objective PSU reviews at reputable sites such as www.jonnyguru.com or www.hardwaresecrets.com on the EXACT model PSU that you are interested in as some brands have good and poor quality PSUs.
You can also get an accurate rating of how much PSU power is required for your current or future system at the PSU calculator link below. Once you know the total PSU watts required then you need to confirm that the 12v rail has enough amps. to support your Vid card(s) and the rest of the PC system.
There are several websites that show the Vid card power consumption in watts. Divide the watts by 12 to determine the amps. required on the 12v rail(s). Add 15 amps for the rest of the PC on the 12v rail and you now know the Minimum total 12v rail amps required under full load. It's best to have at least 5-10 amps. reserve on the 12v rail available under full load so the PSU is not loaded to 100%.
It's also worth noting that people often misunderstand the 80% power rating. This is a rating of the PSU's energy efficiency not it's output. 80% plus PSUs use less grid power to produce the same PC power. If it's 80% Bronze, Silver or Gold the cost savings on electricity is pretty small between Bronze, Silver and Gold unless you are paying very high rates for electricity so any 80% rated quality PSU is fine even if not Gold. For those who leave their PC on 24/7 a quality 80% PSU is a good investment.
The corsair is a much better PSu than the Xion and would work well for you.
That being said the Xion has reports of not being able to supply enough juice to power up a 5870x2 rig so if you can return it you just might want to.