Performance: AGP vs. PCI-E

When a motherboard had both PCI-Express and AGP in the past, the AGP port was implemented more as a hack, than a solid solution. One PCI (not PCI-Express) port was taken and connected to a PCI-to-AGP bridge chip which translated all signals. The major issues with this solution were that the bridge chip added big latencies to the bus and important features like Sidebanding and Fast Writes could not be implemented since they are not supported by PCI. Also the PCI bus is limited to 133 MB/s max. transfer speed, so these "AGP" ports were also limited to 133 MB/s, not much compared to 2.1 GB/s of a real AGP 8x port.

In order to determine if performance of the AGP port on the ULi M1695 is really working as advertised, we used a Radeon X850 Pro AGP and a Radeon X850 Pro PCI-Express in various benchmarks.



It is interesting to see that actually the AGP card seems to be a little bit faster. This could be caused by measurement inaccuracies or different memory timings in the VGA BIOS. However, what we wanted to verify, that AGP is a native implementation with excellent performance, has been proven to be correct by these benchmarks.