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What are the differences? - 2 HD 6870

Last response: in Graphics & Displays
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January 29, 2012 2:48:31 PM

Hi,

After asking here and in some other forums, and reading about it a lot, I decided to CrossFire my HD 6870.
That is my system:
AMD Phenom II X4 955 (probably going to be overclocked to 3.8 or 3.9 GHz)
GA-890GPA-UD3H
G.Skill F3-12800CL7D-4GBECO (going to add one more set like that with the graphics card, so 8GB)
SAPPHIRE HD 6870
Caviar Black 500GB
Corsair HX 850W
ZALMAN Z7 Plus

I don't know what to buy... I want to minimize as much as I can the chance for problems and issues, so I prefer the cards to be exactly the same. Unfortunately, my reference model is no longer available in my region. I'm talking about this card: http://www.sapphiretech.com/presentation/product/?cid=1...
I will probably need to CrossFire it with that card: http://www.sapphiretech.com/presentation/product/?cid=1... (Could it be that it doesn't come with a crossfire bridge? I already have one, but that's kind of odd)

Now what are the differences? Could it cause more issues and problems than expected because they are not exactly the same?
I know that OpenGL is no longer an issue due to new drivers, and I believe that the outputs does not really matter as well, but what about the cooling? different temps can cause some trouble? and what about the PCB? I'm sorry if I sound stupid, I don't really know what I am talking about but I heard that non-reference designs have different PCB's and stuff like that, does it matter for Crossfire?

Thank you all very much! :) 

Sorry I forgot just one last question: I heard something about on-board GPU's (and APU's) using the system RAM for their VRAM, so I thought, can I make my 2xHD 6870's "take" extra VRAM from the system RAM?
Sorry for all of my questions, thanks in advance!

More about : differences 6870

January 29, 2012 3:32:01 PM

It looks to me like the only real difference is the cooler on the cards. They should work find together.

About your second question, a game that needs more RAM than what is available on your card will use system memory. System RAM is slower than the RAM on the card, but the game should automatically use the RAM.
January 29, 2012 3:32:44 PM

While I agree, you should try and match your cards, it is not necessary. As long as you use two 6870s XFire should work. Mixing non-reference and reference versions of the 6870 will still work. You only need one XFire bridge.

Only onboard video devices require the use of system ram DIRECTLY. Like said above, system ram will be used automatically if necessary but it is much slower. Your 6870s don't use system ram in the same way that onboard graphics use system ram. The 6870 has its own dedicated vram which is must faster and better than if the chip had to use system ram. Your 6870s and their 1gb of vram should be enough for gaming at 1920x1080 and below. For eyefinity resolutions most people choose cards with 2gb or more of vram. The ram does not combine on the cards - each card can only use its own 1gb.

So to answer the questions: Yes, XFire will work with those two cards. And No - it would not make any sense to try and make your 6870s use the system ram as vram directly.
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January 29, 2012 3:37:42 PM

Thank you both very much! :) 
I asked about the RAM because I am afraid that maybe even in the near future 1GB of VRAM will not be enough for modern games at 1080p.
If the game/application automatically uses system RAM when needed, so 1600MHz is better than 1333MHz right? it should work better...
January 29, 2012 3:53:39 PM

notavailable said:
Thank you both very much! :) 
I asked about the RAM because I am afraid that maybe even in the near future 1GB of VRAM will not be enough for modern games at 1080p.
If the game/application automatically uses system RAM when needed, so 1600MHz is better than 1333MHz right? it should work better...


Yes the 1600mhz ram is slightly faster. This isn't very noticeable though, it's the kind of thing that shows up in benchmarks but hard to notice in the real world.

Yes, some people report that even at 1080p they are encountering vram limitations with ultra-resolution textures and lots of eye candy with 1gb. Really, I wouldn't worry too much. 2 x 6870 will do extremely well @1080p, I think you'll be happy.
January 29, 2012 3:56:59 PM

OK thank you I appreciate all of your help!
By the way, How do I choose best answer?
!