maverick77_uk

Once upon a time, video cards were PCI, and shared the same bandwidth as all the other devices in your computer, such as modem, soundcard etc. This meant it was slow, and had to wait its turn to send info to the CPU. Thats why these cards are best avoided, unless you have no AGP or PCI-express slot

Then, on a bright sunny day, some bright spark decided to give the video card its own com port, as the GPU's were getting faster and needed a dedicated info-link with the computer - welcome to the advent of the AGP card.

The original specification was AGP 1, that was 1X (surprisingly!), and later 2X. Then came AGP 2, that was 4X. All of these use 1.5V signaling (as far as I'm aware). The AGP2 4X can still signal at 1 and 2X - it can go up to 4X in speed. No real probs up to this point. Except a few glitches, like different AGP slots - AGP professional, which did use different voltages but due to key notches on the cards and in the slots, you can't physically connect most of these cards to the wrong slots, so I won't go into that! except, if you have a universal AGP card that can plug into anything, so depends what chip and circuitry is on the card.......but I digress from the story......

Modern AGP is the AGP3 specification, that can signal at 8X, 4X, 2X and 1X. It however signals at 0.8V. All AGP3 video cards HAVE to be tolerant of 1.5V, so if you plug a AGP 8X card into a AGP2 4X slot, it won't damage anything. Some AGP3 8X cards accept the 1.5V signalling from the AGP2 4X slot, and work fine. Others are not, and so don't work. Therefore, if you're planning on plugging a new graphics card into an older mobo with a 4X slot (AGP2), check out the compatibility of the exact make and models of the card and Mobo you intend to pair - some work, other don't. The only sure way to get a nice shiney new graphics card to work is to plug it into a AGP3 8X slot - coz thats what it was designed for.

For example, I have a AGP2 4X Mobo happily running an AGP3 8X PixelView GeforceFX 5200 card.

If the AGP3 8X card does work in the AGP2 4X slot, the card will work at the 4X speed of the slot.

BEWARE, however, although newer graphics cards are tolerant of older Mobo's, the reverse is not true. If you plug an old AGP1 or 2 card into a new AGP3 8X Mobo, the card will try and draw too much voltage from the slot, and it could damage the card and Mobo.

Finally, the new PCI-express is the new standard, which is a completely different shape slot to AGP, so no probs there......

Hope that clears a few things up! Its therefore not the SPEED of the slots thats incompatible - its the signalling voltages of the newer AGP3 - although, as stated, some cards are tolerant and work, others are not.

See ya.