As a general rule, our belief is that pairing two slow-performing cards using SLI or CrossFire is a bad idea—you’re usually better off running a single faster card. However, the Radeon 4850 X2 delivers astounding performance compared to the single-GPU boards in its price range, spanking the Radeon 4870 and the GeForce GTX 280, with none of the pitfalls that have plagued dual-GPU boards in the past.
At the heart of the board is a pair of ATI’s RV770 GPUs running at 625MHz, just like the single-GPU in the 4850 boards. Each GPU features a full complement of 800 stream processors, which are connected to identical 1GB GDDR3 frame buffers running at 993MHz on a 256-bit bus. Although X2 boards are labeled as featuring 2GB of memory, because the contents of each GPU’s frame buffer must be mirrored, applications can utilize only 1GB of video memory.
Like its 4870-powered predecessor, the 4850 X2 sports ATI’s advanced video decode acceleration, allowing you to view fully accelerated picture-in-picture Blu-ray discs. It’s fully compatible with multiple-monitor displays, and we love that this board features four DVI ports for multi-mon madness.
In our performance testing, the 4850 X2 unseated the fastest single-GPU videocards, the GeForce GTX 280 and Radeon HD 4870, in almost every benchmark. The exception to the rule was Crysis at high visual-quality settings and high resolution. When running at 1920x1200 with 4x antialiasing and the visual-quality settings cranked to Very High, we hit the 4850 X2’s memory bandwidth wall. Despite running at a higher clock speed than the 4870-family boards, the GDDR3 on the 4850 transfers half as much data per clock cycle.
With a street price that’s less than $300, the 4850 X2 is a great deal for owners of lower-resolution 22-inch monitors. However, if you use a 24-inch or 30-inch panel, it’s probably worth ponying up for a card with a peppier memory pipeline.
Killer performance for $300. Four DVI ports! Faster than a GTX 280.
GDDR3 hurts memory bandwidth. Four DVI ports leave no room for rear exhaust vents.
Sapphire 4850 X2
Radeon 4870 HD X2
GeForce GTX 280
Crysis 4X AA/Very High (fps)
Crysis No AA/Very High (fps)
Call of Duty (fps)
Far Cry 1920x1200 (fps)
Far Cry 1680x1050 (fps)
Vantage Game 1 (fps)
Vantage Game 2 (fps)
Best scores are bolded. Benchmarks are run on an Intel Core 2 Quad Q9770 Extreme, with 4GB of memory running Windows Vista. Crysis, and 3DMark Vantage are run at 1920x1200, with 4x AA and 8x anisotropic filtering, unless otherwise noted. Call of Duty is run at 2560x1600 with 4x AA.