How does a PCI slot differ from an AGP slot?

Answer 1

Prior to the current PCI Express slots, most peripherals were connected to a PC via PCI slots. PCI is a shared bus. These peripherals could have included a graphics card, a network 10/100LAN card, a sound card, a MIDI card etc. Intel first introduced boards that could connect a graphics card separately through a dedicated slot called an Accelerated Graphics Port (AGP).

So only a compatible graphics card could be connected there. This was done for performance/bandwidth reasons where AGP provided more performance/bandwidth when compared to a PCI slot.

However, with the introduction of PCIE, where lanes and generations provided leapfrogging performance, AGP was obviated on the platform as the cost of supporting an extra port outweighed the benefits of a universal standard slot that could accept any peripheral, not just graphics cards!