Radeon R9 280x power from 2008 mac pro

[Jasper6120]

Hi all

I need to upgrade the graphics card in my 2008 mac pro 3.1. I was looking at the Radeon R9 280x or the Radeon R9 280. The 280x uses one 6 pin and one 8 pin connector and the 280 uses two 6 pin. With the stock psu in my computer will I be able to power either of these units properly? Also, will it be safe to use the 6 pin connector for the 280x until an 8 pin arrives in the post? I was also looking at the older 7970 cards, would that be more compatible with my machine? Any advice would be great.

Regards

Jordan

 

[Jasper6120]

Hi all. I bought and installed the Radeon R9 280x card in my computer and.... it doesn't work very well. I'm getting very low fps. 10fps compared with about 40fps from my gtx 660ti. I'm running yosemite. What could be going on? I really need help because I'm not very good with this sort of thing and wouldn't know where to start. Do I need another power supply to give this card a boost?

 

[pastrychef]

The two auxiliary power connectors in the Mac Pro are rated to provide up to 75W of power each.

On video cards, 6 pin power connectors are rated to pull up to 75W each and 8 pin connectors are rated to pull up to 150W.

That being said, many people use video cards with 8 pin power connectors in their Mac Pros. When/if these video cards pull too much power, the Mac Pros will usually shut down on its own.

As to why you are seeing poor performance, you need to give more info. What are you running where you are seeing poor performance? What operating system are you using?

 

[pastrychef]

I suggest you go to the following thread for more info:

https://forums.macrumors.com/thread...-boot-screens-pci-system-information.1808938/

 

[Jasper6120]

I've been using this flight sim called War Thunder. The way the graphics are behaving is kind of unusual. When there is scenery, even the tinyest bit of scenery in the peripherals of view the frame rate hovers at about 10fps. The instant the scenery goes (when I'm flying over water) the frames jump to about 170fps. This is on the lowest setting. Its fair that scenery drops the frame rate but I've never seen it anywhere near this extent. The power supply in my mac 3.1 is rated at 980watts. Here are some more of my computer's specs. I really hope I can nut this one out!!

OS: Yosemite 10.10.2
Processor: 2 x 2.8Ghz Quad-Core Intel Xeon
Memory: 12GB 667MHz DDR2 FB-DIMM

System Report on graphics/displays:

AMD Radeon HD 7xxx:
Chipset Model:AMD Radeon HD 7xxx
Type:GPU
BusCIe
Slot:Slot-1
PCIe Lane Width:x16
VRAM (Total):3072 MB
Vendor:ATI (0x1002)
Device ID:0x6798
Revision ID:0x0000
Displays:
E2711:
Resolution:1920 x 1080 @ 60 Hz
Pixel Depth:32-Bit Color (ARGB8888)
Display Serial Number:204INEW2C476
Main Display:Yes
Mirror:Off
Online:Yes
Rotation:Supported

I'd love to hear any ideas.

Cheers

J

 

[Jasper6120]

I should also mention that this card isn't flashed. But none of my cards have ever been flashed and they all have worked, just without the boot screen. I have also just read elsewhere that people are using this card in macs with the internal PSU. So it must be something else that is amiss.

 

[pastrychef]

Even unflashed, it should not be performing so poorly. Power should not be an issue. Like I said lots of people run this card on the internal power of the Mac Pro. If it were drawing too much power, you'd probably see the Mac Pro shut down on its own.

I'm stumped. It doesn't make sense.

 

[Jasper6120]

I really can't seem to figure out the issue. I have everything up to date. I bought the 8 pin power lead from a chinese store and maybe its wired wrong? I would imagine that would just mean it wouldn't turn on at all though...

 

[Jasper6120]

Still chipping away at this issue. My next guess is that it could be the power cable that I bought. I have read that sometimes the power supply cables can be wired differently. I would assume that this would lead to the card not working at all rather than working sluggishly. Currently I have no ways to test that though. Here is the 8 pin cable I purchased to run this card: http://www.ebay.com.au/itm/281675169292?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT