I don't know how knowledgeable these forums tend to be on matters of overclocking, but hopefully someone can help me figure this out.

Just built a new PC, important specs for my question being: i5 3570k; XFX 6870; Corsair CX 500W.

I thought 500W would be more than enough for just the one 6870 as it's not a very power hungry card (http://www.legitreviews.com/article/1605/15/) but once I decided to overclock the card a little (haven't OC'd the CPU yet), I had some interesting results in 3D Mark 11. As expected, my graphics scores went up significantly at a very modest OC from stock 900 Mhz core/1050 Mhz memory to 950/1100. Haven't touched the voltage. However, my physics scores also went down significantly, in the realm of -10%. Since the physics tests are mostly CPU dependent, the only explanation I can think of is that my PSU is already close to maxed out, so when I overclock the video card not enough power is delivered to the CPU.

Any thoughts? It's a decent, if on the budget side of the spectrum, power supply from a good company, and 500W should be more than enough to leave some room for some light overclocking.

The CX 500 is specced at about 400 Watts on the 12 volt rail ( which pretty much all thirsty components use )

While that isn't the 500 watts you'd think the name implies , it should be enough as long as you dont tamper with the voltages.

I'm a bit rusty, but increased power consumption usually comes from increasing the voltage on the component, it shouldn't have gone up more than one or two dozen watts from just increasing the frequency's. ( not entirely sure though. )

And even if it did, the symptoms wouldn't be decreased performance, the psu would most likely blow up, or shut down.

Always overestimate how much headroom you'll need when choosing a PSU. If I were you, I'd save up for a quality 700-750W PSU and not have to worry about any more issues when OCing.

@Ravenlight: I thought I did that when getting 500W for a 1 GPU system.

Oh well, I guess I'll keep overclocking a little at a time and see if that trend continues. I really shouldn't need 700+ watts for my system, even with a little overclocking.

If you just built a new computer to todays specs, then you shouldnt need to overclock yet. Most games can be played at max fps, on high on a $800 dollar computer, without overclocking.

@Jimmi: as i said, if the psu cant cope, the symptoms wont be 10% less physics performance.

@Dagbiker: It's more just because I can rather than for performance. Why else would you buy the unlocked version of a CPU? Besides, I'm still a fair ways away from maxing The Witcher 2... really want to enable that Ubersampling or whatever it is.

@Devildoll said:

@Jimmi: as i said, if the psu cant cope, the symptoms wont be 10% less physics performance.

Point taken. The physics score doesn't mean just a physics test though, it is a test to benchmark your CPU as a whole that uses physics as a measuring stick. Unless I'm missing the point of 3dMark all together.

@Jimmi: Thats Fair.