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Radeon R280x PSU Query

BrynS

BrynS

BrynS

Associate
Joined
26 Nov 2003
Posts
523
Location
Wales, UK
Howdy,

It's been ages since I've upgraded by rig and I feel pretty out of the loop in a few areas. The Radeon 6950 I had in my ancient rig (2.8Ghz Phenom II X6, 8GB RAM) started causing artefacts and reboots a few months ago so I reverted to my previous Radeon 4850, which struggles with most recent gaming on my monitor (HP LP2475w - 1900x1200 native resolution).

I've been looking at getting a Radeon 280 or 280x (probably one of the Asus models) to keep it going until I replace the entire rig with an Intel set up next year. I know that the Radeon 280s and 290x are pretty thirsty power wise so am wondering whether or not my PSU from 2008 (Enermax Pro82+ 525W) is up to the job?

I see that both the 280/280x and 290 need both a 6-pin + 8-pin PSU connector. My PSU has 2x 6+2P connectors but no native 8-pin connector. Will the 6+2Ps suffice? I've used the Enermax PSU calculator on their site to work out my rig's total power usage and it falls within the limits of the PSU with an R280x.

Also, assuming my PSU could handle a Radeon 290 and accepting that my rig would be extremely CPU limited until I upgrade the rest of the system, is it worth stretching an extra £80-100 get a more capable (i.e. 64 versus 32 ROPs, 512-bit bus, Trueaudio, etc) Radeon R290 now? I know the 280s are decent but the underlying architecture is pretty old.

Cheers.
 
the 6+2 are the 8pins
wow 6 years old PSU not bad, and it could run the 280 also, if you are planning on changing psu 600-650 is enough, if you think you could crossfire 2 of them if you find 2nd hand 280 for cheap, i would invest in a 850 PSU, gives you quiter psu you and an open option to crossfire if you ever find a good deal on a 2nd GPU
 
Thanks for the clarification.

Yeah, the PSU has served me well so far -- I've always had good performance and reliability from Enermax PSUs. If it can tide me over until I replace everything next year I'll be happy.

Reckon I'll underclock the 280 just to be safe though and to keep noise and temps down.
 
power consumption of the R9 280x around 250watts, so the system should be around 400-450 watts, no need to downclock it
 
Aah righto.

I've run the PSU calculator on this site again to conservatively account for all my internal cards, fans, HDD, SSDs, etc and its calculating 518W total usage under load with a 280x which seems a bit tight (although the PSU has 580W peak power according to the specs) so I thought I'd downclock a bit to reduce power draw.
 
I do have an overclocked 280X (1.2V 1180MHz) and a heavily overclocked 3570K (4.5 to 4.8GHz relative to my mood) and even though I have been trying to find a reason to upgrade my ancient Corsair HX520 I could not find one. The power consumption of the Tahiti XT2 chip is high but not that high and usually a system is not symmetrically fully loaded at any time so even if your system overall maximum potential power consumption is 500W, rarely the system will go over say 400W. It is always good to have a nice stable PSU that is loaded at most 70-75% but it should be totally fine.

Also downvolting results in a lot greater power consumption savings than downclocking as the power of an IC is related to its combined internal capacitance C, the frequency F and the square of the voltage V.

P.S. The power consumption of R9 280X and R9 290 is similar but I would not pay the premium for the Hawaii, it is a special GPU having special needs and I would not bother. If it's for 1080p gaming either stick with 280X/770 (which is more than enough for pretty much anything maxed out at 1080p) or go for a 780.
 
Cheers. Yeah, downvolting is something to consider although I'm a bit wary of flashing a new card with a different BIOS or is it more straightforward these days? It seems like one can adjust the voltage on MSI cards via the Afterburner software, although as mentioned I was leaning towards the Asus ones with their custom PCBs and better cooling solution (less reported whine, etc).

I'm going to give a 770 some serious thought as well -- haven't run an nVIDIA card since the original Geforce DDR. Power consumption and noise/temps look good too. The only downside seems like the 2GB framebuffer for that sort of outlay. Decisions lol.
 
The frame buffer difference is not significant as on the resolutions both cards will start dying off, more memory will not help. The Asus is controlled via Asus's software GPU Tweak and it is possible to undervolt it. Pretty much everything else is undervolted via Afterburner if its VRM controller allows voltage adjustments at all. The VBE7 route is not that difficult either and if every effort to change the voltage in software fails, it's a last resort.
 
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