- Tom's on PCI Express
Tom's Hardware has posted an interesting article called "PCI Express' Future Promise for Graphics". The longish article talks in detail about PCI Express and its advantages over PCI and AGP buses as well as what both nVidia and ATi will need to do to make the new bus standard a success later this year. nVidia's HSI bridge which is used to provide top to bottom PCI Express graphics cards support at launch is covered very well specifically.
For many prospective buyers, a simple graphics card upgrade with a AGP model will therefore surely be the preferred (read: less expensive) solution. Since this is the case, the chipmakers would suddenly have to design, manufacture and advertise two versions of the same chip, one each for AGP and PCI Express. Considering that a chip tape-out is anything but cheap, it would be logical to focus development of new chips for he PCI Express versions. Should there be demand for an AGP version, it could be implemented by using a bridge chip, which would be far less expensive than creating a second version of the same chip. NVIDIA has all its bases covered, since it had the foresight to design its bridge to work in both directions. This way, it can either link a PCI Express chip to an AGP bus or vice versa. In effect, the HSI bridge allows NVIDIA to present a full complement of PCI Express cards right from the start with very little financial input.