Typicaly it is 8x but on older computers it can range from 4x, 2x, and 1x.
AGP is an older video card specification that had a higher bus speed than the PCI spec.
PCI Express 2.0 x 16 is the Fastest But PCI Express x16 is faster than AGP
The 8X represents that the card card process 8 times the number of transfers per clock compared to the original 1x cards. So, it directly relates to the speed through the AGP bus. 8 times the bus speed.
PCIe
Accelerated Graphics Port (AGP)
There is no latest AGP bus. The most recent bus designed for high performance equipment is PCI-E. And x16 has the highest bandwidth.
AGP (Advanced Graphics Port) Is a special card socket designed specifically for video cards. Video cards used to sit on the PCI bus with all the rest of your hardware. It was eventually decided that performance could be improved by putting video cards on their own specific bus. The AGP bus has special priority when the CPU is processing stuff, and usually runs at a much higher clockspeed than the PCI bus.
32 bit
PCI Express
Video Card
PCI-E
The IDE drive has no direct correlation to the AGP bus.