apg slotOlder Expansion Slots on Motherboards 1. AGP Slot. Stands for Accelerated Graphics Port, this slot is available only in older motherboards to connect the graphics card for accelerating 3D output. AGP offers fasterI started a thread about another odd type of motherboards, Socket 423 and 478 motherboards with the universal AGP slot which are not as common as their 1.5v keyed only