I have a reference MSI 7970 and will be purchasing very very soon a second reference 7970.
Howoever the current price for another MSI 7970 is about 90$ more than other brands such as Sapphire, HIS etc.
I plan to do 120hz gaming + 3D gaming and in my research attempts have come across varied perspectives on compatibility/problems:/
1. Some people say it always works (reference or non-reference), regardless of Brand
2. Some people said it had to be both reference or both non-reference for both cards, regardless of Brand
3. Some say it has to be the same brand no matter what
Can anyone help clarify these varied responses. Preferrably i'd like to buy the cheaper Brand such as Sapphire/HIS, but if it causes problems for 3D gaming/drivers/120hz then i have no choice but to get another MSI 7970.
Or will these problems still persist even if i get two MSI 7970 reference cards?
AMD cards can crossfire with any card of the same first two digits in the same series of cards.
7970's can crossfire with any other 7970 or 7950, and if a 7990 is released, that will also work for tri-fire.
That said, it is generally advisable to have them be the same model. All reference boards should have no issues at all, but if you have different HSF, it can be troublesome to use MSI Afterburner, as you can only have one fan profile, and they often prefer very different fan settings, so you may lose some fine tuning abilities. I have also found that I had troubles OCing different cards with MSI afterburner, but that may have been user error. I've recently figured out how to do it with Nvidia cards with different stock clocks.
Now, here is the thing, Nvidia 3D Vision (2) is generally considered easier and overall a better experience than HD3D from AMD. Until very recently, AMD did not support crossfire with HD3D and I'm still not 100% sure it will work (they promise things and sometimes it gets delayed on being implemented). If you haven't purchased your monitor, you may want to consider going the Nvidia route.
I already have a MSI 7970, so going the Nvidia path will not be considered at this point until my next upgrade (year or two).
120hz gaming will be my primary focus (3D gaming isn't at 120hz is it?) for Battlefield 3 - and i believe that game supports it natively so.. that should reduce some problems associated with it (once again i only think this).
Here is the thing, how often do you upgrade or change your monitor? Your monitor is likely going to choose what you use for the next several upgrades, so if you go with a monitor good for AMD systems, it won't be good for Nvidia, and visa versa.
Anyways, HD3D isn't bad, and for the most part, gives very similar results. It just isn't as easy to use and a little more likely to have support issues. You also will need 3rd party software, either tridef or iz3d (some monitors come with the software).