Is the PSU enough?

[Mackingzie]

Specs:
Corsair - GS 800
AMD 8120 (overclocked to 4Ghz from 3.6Ghz)
Corsair RAM 8GB (x 2)
Radeon R9 280X (x 2)
Motherboard: Gigabyte Ga-990FXA-UD3

So the question is can I overclock one of the graphichs cards? Or am I att my limit?

 

[madmatt30]

You're clear by 150w
There's some headroom for overclocking - never tends to work that well on a cf setup though in all honesty - you generally want both cards at the same or very similar speeds.

 

[birne]

800 watt is pleny of power, even if you are running 2 280x
the actual power draw is probably way less than 800 even at full load

 

[Mackingzie]

You're clear by 150w
There's some headroom for overclocking - never tends to work that well on a cf setup though in all honesty - you generally want both cards at the same or very similar speeds.

Why do you want them at the sam speed? Power struggle?
How do one usually calculate the power draw?

 

[4745454b]

While not exact, it's generally safe to use the "TDP" figures from the manufacturers. The 280 is a 225W part, and the 8120 is a 125W CPU. This is 575W total. I generally add another 50W for the drives, ram, board, etc. So draw is somewhere around 625W. Gaming is probably less then this as most 280s are closer to 200W, but we need to plan on "worst case". (gaming doesn't tax the GPU and CPU to 100% all the time.) At 625W you are looking at most of what an 800W PSU can do safely. I'll load a PSU up to 80% or so of it's output and you are just about there. OCing the CPU or GPUs can put you over that 80% mark so I'd either not OC, or look into getting a bigger PSU.

 

[madmatt30]

Mackingzie - the idea of crossfire is to put a simultaneous equal load on each card not use each card independently.

2 years back the amd drivers actually auto down clocked the speed of a faster card if 2 non matched cards were used.
Nowadays you absolutely can use mismatched cards & speeds but the fact us it makes absolute sense to match core speeds reasonably closely.

Don't bother even considering overclocking ram speeds on your bottom card either because that vram is not utilised at all.