Comparing nVIDIA and ATI's Approach to PCI-Express
ATI, which has been nipping successfully at nVIDIA's heels over the last year or so with its high-performance RADEON series, sometimes beating nVIDIA in competitive benchmarks, uses a native solution in its X-series of PCI-Express GPUs and cards.
Thus, it appeared initially that from an architectural standpoint, the two biggest GPU makers had come to opposite conclusions about which approach is the best for moving to PCI-Express. However, the newest nVIDIA GPUs, the GeForce 6 series, use a similar approach to ATI. The 6800 series of GPUs integrate the HSI on the GPU, while the new 6600 series finally makes the move all the say to native PCI-Express parts. Because it will be a long time before PCI-Express (also known as PCX) replaces AGP 8x, some GeForce 6 GPUs use the HSI chip to convert the GPU for use on AGP 8x graphics cards.