Will my OCZ StealthXStream 600W be enough?

The general rule of thumb is a high quality 500 to 550 watt power supply with sufficient current (amps) on the 12 volt rail(s) can easily power a system with any single video card made. A high quality 700 to 750 watt power supply with sufficient current (amps) on the 12 volt rail(s) can power a system with two video cards operating in dual mode. There are a few exceptions like the new ATI Radeon HD 5XXX series cards which use less power due to their energy efficiency.

The recommendations are for an entire system.

Corsair, PC Power & Cooling, and Seasonic are some of the brands that have a reputation for high quality power supplies that consistently earn high marks in technical reviews. They are reliable, stable, and come with a 5 year warranty. Lately we've been seeing a few other brands offering some high quality units.

I had a look and my power supply has 18A on each 12v rail.

How do I find how many amps I require for 2x HD4850's?

I had a quick google but I can only find forum posts ranging from 8A to 12A for a single HD4850. If it's 8A then I'm fine but otherwise I'm going to have to upgrade.

I've looked on ATI's website but the specifications are vague when it comes to power supply requirements.

On the HD4850 specification it says I require 550W for crossfire but in their list of recommended power supplies there aren't any that are below 650W.


I know which power supply I want (Corsair TX 750W) if I was to upgrade but I'd rather avoid any unnecessary expenditure.

System power consumption with one 4850 video card during a gaming session:

http://www.tomshardware.com/reviews/radeon-hd-4850,1957...

System power consumption at load with two 4850 video cards in Crossfire mode:

http://www.anandtech.com/video/showdoc.aspx?i=3341&p=22

The results are pretty consistent with a Tom's Hardware article published last January about power consumption during gaming sessions. Gamers typically don't go over 300 watts total power consumption. There are some exceptions though.

The current (amps) that a video card requires is a bit more problematic. Most technical reviews only test total system power consumption at the wall outlet (mains). I have the information referenced but I'm not at home right now. I can check later and post the link.

Thanks for the advice.

I think this could just be a case of trying it to find out.

Out of curiosity, if the power supply isn't enough after adding a second card, what would be the worst case scenario?

Would it kill any of my components?

or would my power supply just stop working till I turn it off and back on again?

A good PSU will simply electronically shut itself off. A bad PSU can fail catastrophically. Translation - burst into flame or explode.  

Ah I see, now you have me scared.

What is it that makes the PSU explode? Is there something I can look for on my PSU that will tell me?

Dang Blasted! I could have sworn I bookmarked a web page page showing power consumption of individual pc components but I can't find it. One of the respected web sites that does technical reviews now has electronic measuring devices which allows them to do that instead of just total power draw at the wall outlet (mains).

Thanks for looking anyway.

I think my PSU shouldn't blow up if I ask too much of it so I'm going to give it a shot.

If however I do require a new PSU, I was thinking of getting a Corsair TX 750W but is it worth spending the extra £15-ish for the Modular HX 750W?

I figure I should spend around £100 on a decent PSU now so that it will last me 5 years or so and allow me to upgrade to say a pair of HD5850's/HD5870's when they come down in price in the future; most probably this time next year when I do a complete re-build.

Yes, the Corsair power supplies are worth the higher price. They are high quality power supplies that consistently earn high marks in technical reviews. They are stable, reliable, and come with a 5 year warranty.

OCZ, while not being the best power supply make, is decent. I highly doubt your power supply will burst into flames if too much is asked of it. And yes, like JohnnyLucky said, Corsair power supplies are worth the higher price. And to add the the recommended list, Antec makes very nice PSU's as well.

This might be the article you were looking for johnnylucky. An excellent article showing actual use by different components. It's worth a read for anyone who hasn't read it. "PC Power Consumption: How many watts do we really need?"

http://www.xbitlabs.com/articles/coolers/display/system...

To OP, you'll need to use an adapter that is included in most GPU boxes, but i'd run the OCZ 500w StealthStream.

dirtmountain - very nice article. I just added it to my references. Thanks.

I was thinking it was an xbitlabs article but that's not the one. I'll have to look through their web site and see if I can find the one I'm thinking of.