Question: Does Intel 845 series (P4i45D / P4i45E / P4i45GL / P4i45GV / P4i45PE / P4i45G / 775i45GV) chipset support 3.3V AGP card?(10/29/2002) Answer: Intel 845 chipset supports 1.5V signaling AGP cards only and the AGP slot on motherboard got 1.5V key in it following the AGP specification in order to prevent a 3.3V AGP card from being plugged in. However, it turned out some AGP adapters operate at only 3.3V signaling level, were notched at the 1.5V key on the golden-finger interface.
When using these cards, if the Vddq and VCC3.3 signals are shorted on them, will break up the north bridge as the Vddq is raised from 1.5V to 3.3V instead. In other words, the motherboard will be permanently damaged as a result as soon as the system is powered up with such an AGP card. According to AGP specification, AGP4X mode will work at 1.5V signaling level only. If your AGP card has the 1.5V notch as
illustrated in the user's manual but it cannot support AGP4X, please check with your card provider or manufacturer whether it can operate at 1.5V signaling level.