Only if it has the proper keying. Some 8x cards do, but many do not.
Bandwidth.
The best way is to E-mail your pc mfg. and ask what your motherboard uses.
No it won't work!
For the most part AGP 8x Cards WILL NOT work with a AGP 4x slot. The motherboard will only supply 1.5 volts of power to the card leaving the other half with no power and will not work properly.
As long as you have the expansion slot (PCI, APG, PCI-Ex) available; Yes you can.
yes
Yes.
AnswerYes.Added:Sometimes! Not all AGP 1x or 2x video cards will have the same connection type as 4x or 8x cards, some older cards will not physically fit in the slot for modern motherboards.
All 8x AGP slots are backwards-compatible with 4x cards, so there is no reason you couldn't use a 4x card, except that it's slower. Most 8x cards should work in a 4x slot as well, but they won't be able to run at their full potential, and a few may have trouble running at a lower speed (NVIDIA cards should be fine).
Check you manual for you computer or motherboard. The key is literally where the slot key is placed. If a device has the 1.5V key and claims operation at 0.8V operation then you know that it is capable of 8x speed. This key slot is approximately 1.5 inches away from the registration tab connector that is often used to lock the board in place while in the slot.
If you have an Agpx8 compatible motherboard you will be able to utilize an agpx8 video card if your mother board only goes to 4x then the 8x graphics card will automatically use the 4x setting 8x meaning more information/data being sent is always better .Agpx4 card will work on x8 slot