What is AGP 2.0
AGP 2.0 is a 1.5V AGP slot capable of 4x,2x and 1x speeds.
What is AGP 3.0
AGP 3.0 is keyed like a 1.5V AGP 2.0 slot, but it only uses 0.8V of power. It supports 8X, 4X, 2X and 1X speeds.
Rule #1: Speeds are backwards compatible
AGP Speeds are required to be backwards compatible. This means that an 8X video card MUST be able to run at 4x, 2x, or 1x speeds. However, this does NOT necessarily mean that your 8X card will run on a 4x slot.
Because speeds must be backwards compatible, Signalling Voltage is where incompatibilities arise. Basically:
* All 8x cards are 0.8v AGP 3.0 spec
* 8x cards will fit in 1.5V slots, and can tolerate the voltage, but will NOT run properly
* 4x cards can be either 1.5V or 0.8V
* 2x and 1x cards are either 3.3V or 1.5V
* Except in the case of the 8X cards, using the wrong voltage card with the wrong motherboard can result in damage in card and board
* If you install a card of incompatible voltages with the motherboard's specs, the card will NOT run
The connectors on AGP video cards are keyed in such a way that you can only install equipment that have compatible Voltage keyed connectors. Normally the key of the card determines its signal voltage. AGP 1.0 and AGP 2.0 cards using a 1.5V key will signal at 1.5 volts. However, AGP 3.0 devices can tolerate 1.5V - they won't be destroyed, they just might not work properly.
The Bottomline
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