AGP 4x on 8x Mainboard

[icekin]

A friend recently left me his nice desktop, but its missing the video card. The mainboard is a Gigabyte GA-8IPE775. According to the specs, its needs a 8X video card, but I have another 4x lying around.

Are the mainboards backward compatible?

[ChalkTrauma]

I do believe they are.. I was in a similar situation and used a 4x card in an 8x system. But you have to be careful about voltages.. check out the compatibility notes here Accelerated Graphics Port

[icekin]

I plugged in the 4X video card and got no output. I know the card works somewhat since I tested it on another system. I'm guessing the board is probably busted. Does anyone know if a 8x video card will work on a 4x slot (i.e. is the card backward compatible as well)?

[steeladept]

AFAIK it is supposed to be.  AGP is supposed to be 100% compliant and the 'X' just identifies the bus size (read data throughput from what I have gathered).  That said, the key word is 'supposed' because I have heard of compatibility issues before.

[lanux128]

Does anyone know if a 8x video card will work on a 4x slot (i.e. is the card backward compatible as well)?

i have used an 8x card (nvidia) on a 2x board previously but i haven't tried the other way around.

[nudone]

taken from http://en.wikipedia.org/wiki/Accelerated_Graphics_Port

AGP cards are backward and forward compatible within limits. 1.5 V-only keyed cards will not go into 3.3 V slots and vice versa, though "Universal" slots exist which accept either type of card. AGP Pro cards will not fit into standard slots, but standard AGP cards will work in a Pro slot. Some newer cards, like Nvidia's GeForce 6 series or ATI's Radeon X800 series, only have keys for 1.5 V to prevent them from installing in older mainboards without 1.5 V support. Some of the last modern cards with 3.3 V support were the Nvidia GeForce FX series and the ATI Radeon 9500/9700/9800(R350) (but not 9600/9800(R360)).

It is important to check voltage compatibility as some cards incorrectly have dual notches and some motherboards incorrectly have fully open slots. Furthermore, some poorly designed older 3.3 V cards incorrectly have the 1.5 V key. Inserting a card into a slot that does not support the correct signaling voltage may cause damage.

so, other than the 'slots' preventing you from being able to insert the card it looks like things are pretty compatible.