Crossfiring 2 R9 280xs on a PCIe 2.0 motherboard

[magoojy]

Is it worth it? Is there a noticeable performance hit when compared to PCIe 3.0?

 

[IRONBATMAN]

I don't think so, but both PCIe 16x slots have to be ruining in at least 8x mode. Don't forget a strong power supply

 

[magoojy]

Would a 750 watt PSU suffice?

 

[IRONBATMAN]

250w TDP x2=500w
+ you cpu and all other components such as peripherals, fans, hdd...etc.
guessing ~700w-750w with OC.

 

[Dblkk]

Would a 750 watt PSU suffice?

750w is fine, but a strong psu means a strong psu. Not hypothetical power delivery.

An evga 650w 80 plus gold will deliver more power than a rosewill 850w.

Due to quality of the power supply. the rosewill posted has around 55% efficiency at 50% power usage and gets worse the farther you get from 50% usage. The evga offers roughly 90% efficiency at 50%, and varies slightly the farther from 50% usage you get.

SO, example. 50% usage.
650w evga puts out 585 watts
850w rosewill puts out 467 watts
So even though the rosewill has 200w posted higher on the sticker, it still puts out over 100w less than the evga. Now the rosewill is still using 850W, your only seeing 467.
The evga is a smaller unit, yet still puts out almost close to what its taking from the wall, which is still more than the larger rosewill

 

[IRONBATMAN]

Rosewill does make some good PSUs....

 

[magoojy]

OK, I have a corsair CX750M power supply. I think that should work from what's been posted here.