The AGP connector installed on many Pentium® 4 processor-based desktop boards is keyed for 1.5V AGP cards only.

The AGP connector is not mechanically compatible with 3.3V AGP cards. To some the 1.5V AGP connector might look backwards because of the connector key being exactly the opposite of the 3.3V AGP connector.

AGP 2x/4x Universal Graphics card with AGP 1.5V slot

AGP 2x Graphics card with AGP 1.5V slot

AGP is an effective interface for graphics-intensive applications, such as 3D applications. Based on the AGP Local Bus Specification, Rev. 2.1, AGP is independent of the PCI Bus and intended for exclusive use with graphical display devices.

This applies to:

Intel® Desktop Board CA810E Intel® Desktop Board D815EFV/D815EPFV Intel® Desktop Board D845BG Intel® Desktop Board D845EBG2 Intel® Desktop Board D845EBT Intel® Desktop Board D845EPI Intel® Desktop Board D845EPT2 Intel® Desktop Board D845GBV Intel® Desktop Board D845GEBV2 Intel® Desktop Board D845GERG2 Intel® Desktop Board D845GLAD Intel® Desktop Board D845GLLY Intel® Desktop Board D845GLVA Intel® Desktop Board D845GRG Intel® Desktop Board D845GVAD2 Intel® Desktop Board D845GVSR Intel® Desktop Board D845HV Intel® Desktop Board D845PEBT2 Intel® Desktop Board D845PESV Intel® Desktop Board D845PT Intel® Desktop Board D845WN Intel® Desktop Board D848PMB Intel® Desktop Board D850EMD2 Intel® Desktop Board D850EMV2 Intel® Desktop Board D850GB Intel® Desktop Board D850MD Intel® Desktop Board D850MV Intel® Desktop Board D865GBF Intel® Desktop Board D865GLC Intel® Desktop Board D865GRH Intel® Desktop Board D865PERL Intel® Desktop Board D875PBZ