I've been eyeing up Crossfire with another r9 290. My little wattage metre thing tells me that when playing GTA V it goes as high as 375w. This is with an overclock to 1100mhz on the core of the card and my CPU at 4.6ghz. To me, it looks like I could sneak another r9 290 in there without changing my PSU. Else I'm going to buy the same PSU but in the 850w version so I don't have to remove any cabling. That is how lazy I am. I will need to change the loop around a little. I'm thinking I'm not going to bother watercooling the additional card also. In case you missed the question... (i no use question mark, or phrase question) ... do we think I could get another r9 290 in?
You might be able to get away with it, but it'd be a bit risky. IIRC the 290 cards tend to draw over 200W (TDP is 275W) - I'd say it wouldn't be worth the risk since a PSU blowout could take out everything. If you're feeling more devil may care, then it should be able to 'run' both briefly (even if the peak draw exceeds 650W) so you could test the total power draw with mild gaming (perhaps turn off the OCs to give a margin of error) and then review the readings?
I think the best course of action would be to add the second R9 290 (without changing the PSU), measuring the power draw again, and then only change if you are unhappy with the number. It is not very likely that a PSU of the quality of a Seasonic X series unit would fail catastrophically and cause damage to other components. It is more likely that if the system draws more than it can provide it will just shut down gracefully. Also don't be so sure that you can change the PSU to the current generation X-850 (KM3) without changing the cables as I think the X-660 uses a different modular interface (KM). So I would suggest double checking that.
I'd probably not risk it long term but the seasonic won't explode and take down your components. Depending on age of psu you have Aprox 600watts maybe less. And I'd say you need 10% headroom. So call it 540 watt total that's the max I'd want to put on a 650 watt psu assuming it's under 3 years old. 375 + 200 min is over what I'd say is safe targets.
Yeah, I'm just going to get a 850w Seasonic then and sell the one in there I reckon. Doubt I'll ever need more than 700.
Based on what SeaSonic told me about my PSU you should be good for bursts of up to 800W with your existing PSU. As mentioned above double check the pin-outs on the latest SeaSonic PSUs before using your current cables, on some of them they've reversed the pin-outs on the PCI-E cables. 24 Pin cables remain the same.
I've had a chance of heart. I might get a gtx 980. At my res it's pretty much there and I have way more watts to spare. Makes my loop rebuild easier also.
