In the latest games, the Viper X1600 Pro AGP 512 MB was unable to provide playable frame rates using high-quality settings at even the most basic 1024x768 resolution. This begs the question: "How badly are the AGP interface and older processors holding this card back?" To find out, we located a PCI Express version of the Viper X1600 Pro 512 MB for comparison. Adding a modern midrange CPU insures that both cards receive a sufficient data flow.

To make a fair comparison of the cards, we chose a board that was equally capable in both AGP and PCI-Express performance: the AP9567A reference platform from Uli. Its M1695/M1597 chipset ports both PCI-Express from the Northbridge and AGP from the Southbridge to the CPU via AMD's HyperTransport interface.

AGP Vs. PCI-Express Performance

Because of the second platform's reference board status, we have kept all mention of it separate from our previous performance tests. Individual test scores below aren't directly comparable to those of retail motherboards, but overlaps in interface performance make it adequate to compare similar graphics cards to each other within this narrow scope.

To sample the performance difference between AGP and PCI-Express versions of the card, we chose the three best settings where it failed to average a minimum 30 frames per second at 1024x768 during the previous analysis above:

• F.E.A.R., Maximum Detail at 4xAA/8xAF, no soft shadows
• Oblivion outdoor scene, 4xAA and Distant Landscape enabled
• Black and White 2, high detail plus High AA

Though both cards use the same 500 MHz Radeon X1600 Pro processor and GDDR2-800 graphics RAM, the AGP version leads the PCI-Express version in performance. The AGP advantage is most likely attributed to a slight mismatch in the memory's actual data rates, comprising 810 MHz compared to the PCI-Express version's 784 MHz.

No noticeable performance loss was attributable to the use of an AGP bus or the necessary AGP to PCI Express signal converter; both cards were simply too slow to display reasonably high details even at relatively low resolutions in the latest games.