Frame Buffer: 2GB Versus 1GB
Were you to buy a 2GB Radeon HD 5870 for three-monitor gaming, using the other three displays in a separate display group, you’d probably be curious about the benefits of a 2GB card versus a 1GB board, especially given the price premium.
We ran the same benchmarks at the same settings and 5760x1080 resolution and discovered that simply increasing the capacity of your frame buffer isn’t a guarantee of additional performance. We’ve seen this before, where the overhead of implementing a larger frame buffer causes a small performance hit in certain situations, so it’s hardly a surprise.
To the contrary, this is good news for folks running Radeon HD 5870 1GB boards, because it means they already have the rendering muscle needed to drive three 1920x1080 displays at playable frame rates.
Of course, there is a reason to step up from 1GB to 2GB (beside the obvious output connectivity increase). I picked a couple of the games that were running plenty-fast in the previous CrossFire chart and added 8xAA to them. As you can see, Far Cry 2 is significantly more playable, and Battlefield: Bad Company 2 goes from being a slide show to cranking along fairly smoothly. The key here is that you’ll have to exceed the limits of a 1GB card at settings that’d still otherwise be playable on a 2GB board. The rendering muscle of a second board in CrossFire is instrumental in delivering that extra “oomph.”