Radeon HD 4850 and 4870 CrossfireX -
8 - CF and Dual-screen | The Conclusion
The Dual-screen prejudice
For the users with dual monitors. Both NVIDIA and ATI always have had the limitation that once you enable SLI or Crossfire, you pretty much loose your second screen on which you could expand your (2D) Windows desktop. For example you can not use one screen for gaming while the other shows your windows desktop.
Yesterday a forum user asked me if I wanted to check this out as apparently ATI should have fixed this with Catalyst drivers 8.1. There is a glimmer of hope, but its still buggy and unsupported...
Say you have two cards in Crossfire. Now what definitely will not work is connecting your monitors each to a separate graphics card. We tried, only one primary screen will be enabled in combo with enabling crossfire(X). Then we hooked up two monitors towards one graphics card (4850) and enabled CrossfireX again. Surprisingly, a second monitor can be enabled to expand your desktop with CF activated.
Unfortunately the minute we started playing a game, that second screen went black, and even after exiting the game, it did not come back. So support seems to be partly there yet is definitely not working properly. We see very similar behavior with NVIDIA SLI cards, and I know for a fact that they are working on solving this issue. I hope AMD will do the same.
So admittedly, I'm really becoming more enthusiastic about Crossfire solutions. I do stand by my opinion that after using 2 GPUs (whether that's NVIDIA or ATI does not matter), things often get really tricky due to drivers and actual game support. I'll take it even a step further, I'm really a single-GPU man myself, I like to be monogamous that way :) See, often we see issues. We had it with 3-way SLI, we had it with 3-way mixing and matching among 4800 surely didn't work as the slower card seems to slow down the other two as well. Driver issues, very likely. So if you go SLI or Crossfire, my recommendation really is two GPUs should be the maximum at this point in time for the best experience.
I'll definitely revisit the article once we have a third 4870 in the house though, as that should be really interesting to test. Despite the quirks we also had two titles giving me a headache (Crysis would just not allow CF to kick in even after reinstalling the game and again patching it to v1.2), and Frontlines Fuel of War just simply crashed, we tried three drivers on that one. But that was two out of like ten titles and given that the products are so new I'll forfeit on that for now ... see the rest of the batch have been showing really interesting performance.
The soft-spot money wise are two cards setup in Crossfire. Especially two 4850's kick in as massive value, as for under 400 USD you get to play around with performance better than a GeForce GTX 280, so that's just real value in your pocket right there as you just saved 250 bucks. I mean the GTX 280 is just an astounding card, yet it is getting sodomized badly due to it's high price.
No kidding it is sick how much performance these cards combined can push, the 2-way GPU scaling is just really superb. Crossfire with two series 4800 cards definitely makes more sense than NVIDIA's high-end SLI money wise. On the other side of the scope .. AMD needs two GPUs to do so, two sets of cloned memory and hey .. don't rule out the lower priced NVIDIA cards just yet either. I'm lacking a second GeForce 9800 GTX+ at the moment, yet keep an eye out for another VGA charts update likely next week, where I'll try and include as much results as possible for you to be able to compare even better.
So driver quirks aside, in the NVIDIA SLI review I used Pamela Anderson's boobs as anecdote for SLI (big and expensive, yet a nice pair). For the ATI Series 4800 series I have to refine my choice in women even a little better, yep .. series 4800 Crossfire might be the Jessica Alba in your PC man ... downright sexy. Crossfire seems to scale really well and money wise, this starts to make some real good sense as an upgrade.
Thanks go out to Force3D for supplying additional cards. We'll have another article focused at their cards real soon. That's it for now. Once we have a third 4870 in the house I'll definitely add some results on that combo as well.
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