6850 crossfire?

[SheepBeast]

Hi there

I've currently got an Asus 6850. My mate's brother is ditching his current card (which is also a 6850) due to overheating issues. I'm pretty confident that with a bit of a clean and some new thermal paste I can sort those out. Would it be possible to crossfire his card with my current one (different brands)?

He's said he'll sell me it for £25. Taking into account the chance that there may be a more fundamental problem with the card (which I might be unable to fix), and the microstutter issues I've heard are present in a Crossfire 6850 setup, do you guys think it'd be worth it for me to do this?

I should probably say, I do game a fair amount, and I'm perfectly happy with the performance of my single 6850 as it is right now. It handles everything at max or near max settings at 1080p. I just have to turn AA off which is fine because I don't like it anyway.

 

[Orcvader]

Yup. The 6850 can crossfire with any other 6850, even with different speeds/memory/brand/etc.

It will be a very good boost to your setup, as long as you install the AMD CAPs that will iron out most of the stuttering problems .

 

[opstrat]

What's ur motherboard mate? Check that the 2 pcie lanes will run @ duel x8 and not x16 x4.

Both cards will be fine however the faster of the 2 will only go at the speed of the slowest.

 

[Orcvader]

What's ur motherboard mate? Check that the 2 pcie lanes will run @ duel x8 and not x16 x4.

Both cards will be fine however the faster of the 2 will only go at the speed of the slowest.

Not with the case of Crossfire. Each card will run at their native speeds.

 

[opstrat]

Sorry my mistake. I read differently untill I just tested it with my own 6850's

 

[SheepBeast]

Sweet, thanks guys. Got a good mobo so that won't be an issue, same goes for power supply (I like to overinvest in core components so I have good upgrade options).

What do you mean by "AMD CAPs"? Crossfire and SLI are a couple of the areas of PC tech where I'm least knowledgeable. I know roughly how they work etc, but I've never done it or researched it so I'm not clear on the details

 

[Orcvader]

Catalyst Application Profiles: http://sites.amd.com/us/game/downloads/pages/crossfirex-app-profiles.aspx

Basically helps optimise Crossfire.

 

[SheepBeast]

Cool, thankyou

The other thing I was wondering... I may invest in a new cooler for the 2nd 6850, firstly if reseating doesn't help, plus also for better looks.

My current 6850 is an Asus DirectCU II version. Is it possible to buy a DirectCU II cooler by itself? I guess 2nd hand would be the way to go on that one?

Alternatively, I am considering just buying two of these. I want my system to look homogeneous (yeah im OCD) but that'd be quite a lot of money.

 

[Orcvader]

The Gelid should be better than the DirectCU II cooler, I would get two of those and you should see better temps on both cards .

 

[Rusty0611]

The problem is that with 6850 and 6870 crossfire is that you have considerable GPU grunt (enough to max out most games I would hazard a guess) but you don't have enough VRAM. 1GB VRAM isn't enough for BF3, for example. It's probably the same for other games but I only really have tested VRAM usage in BF3.

The problem with not having enough VRAM is that you can do nothing to counter it other than dropping settings which is what you've already done with 1 6850 and in the end you're basically back where you started with no real benefit.

Something along the lines of this very simplistic model:

1 6850 -> 100% utilised -> 60 FPS
2 6850's -> 50% utilised (due to dropping settings due to VRAM cap) -> 60 FPS

The only way I can see a benefit is if you game at 120hz and therefore you can drop the settings to get closer to 120 FPS for the ultimate smoothness. But, even then, I see miniscule difference in BF3 from running at 80-90 FPS and close to 120 capped. I wouldn't be able to tell the difference if looking at them without an FPS counter. So even calling this particular point a 'benefit' is a push.