Radeon 4670 Performance Preview

So far AMD’s bold new strategy of skipping large, cutting edge high-end GPUs in favor of smaller, more efficient midrange GPU designs, and then scaling that technology up and down the rest of their graphics lineup has paid off.

Their RV770-based Radeon HD 4850 and 4870 both deliver excellent performance in their respective price segments. Their arrival forced NVIDIA to slash prices on their entire GeForce lineup, including their flagship GeForce GTX 260 and GTX 280 GPUs. Despite the GeForce price cuts, this hasn’t stopped ATI from taking share from NVIDIA. And in the high-end of the market, ATI’s dual GPU Radeon HD 4870 X2 is the fastest graphics card in the world right now.

But how well does this strategy scale down? Does ATI’s architecture continue to perform well with half of its functional units (including its shaders), removed? That’s what we’re here today to find out!

Finally, a new ATI GPU architecture for the mainstream segment

Based on ATI’s RV730 GPU, the Radeon 4600 series is designed to replace the Radeon 3600 series in ATI’s lineup. Despite their new name, the 3600s weren’t dramatically different than ATI’s older Radeon 2600 line. The Radeon 3650’s RV635 GPU boasted the same 120-shader architecture as the Radeon 2600, with 8 texture units, 4 ROPs, and a 128-bit memory interface, just like Radeon 2600. The big additions ATI incorporated into RV635 were DirectX 10.1 support and a more energy efficient 55-nm manufacturing process. Every where else the Radeon 3600 GPU was quite similar to its predecessor, and as a result, performance between the two was quite comparable. As you can imagine this put ATI at a performance disadvantage in comparison to NVIDIA’s GeForce 8500 and 8600 lines of GPUs.

NVIDIA must have taken note of this, as their GeForce 8500/8600 replacements, the GeForce 9400 GT and 9500 GT are largely based on their respective predecessors; both the GeForce 8500 GT and GeForce 9400 GT sport 16 stream processor architectures, while the 9500 GT and 8600 GT/GTS are all based around a 32-shader architecture. NVIDIA has incorporated a few tweaks to improve clock-for-clock performance, and the GeForce 9400 and 9500 GT are clocked to higher speeds, but NVIDIA didn’t start with a blank sheet of paper when designing these parts. This lack of innovation in the mainstream segment has kept some gamers on a budget from upgrading their trusty graphics cards like the Radeon X1950 Pro and GeForce 7900 GT.

Fortunately this isn’t the case for RV730, it’s an entirely new GPU that’s designed to address the flaws in RV635…