JUST A FEW months before the official announcements, our oriental colleagues have extracted the first PCI Express benchmarks, enabling us to compare PCI Express implementations from the pair of graphics Tweedledumbos. ATi developed its RV380 chip - similar to the Radeon 9600XT - as a native PCI Express offering. In the tests, it was plugged into a Gigabyte i915G + ICH6Rdemo motherboard. The board enables PCI 16X, and sports two more PCI Express 1X slots, where 1X stands for 250MB - double of the speed of the good old PCI slot. The processor used in the test was famous the 2.8GHz Prescott LGA 775.
The Canadians" PCI Express graphics chip weighs in at 130nm and is supported by 128MB of Samsung 2.8ns DDR Ram. The card is an engineering sample and is clocked at 450MHz. The now elderly Radeon 9600 XT is clocked at 500 or even 525MHz, so we may presume that ATi will increase the clock speed with its next revision of chip.
Nvidia, on the other hand is a using bridge chip to make its AGP chips work with PCI Express and you can imagine that this is inherently slower than a native PCI express chip, since it has to continually translate AGP commands to PCI Express.