Short for AGP in-line memory module, AIMM is also known as the Graphics Performance Accelerator. It is an expansion card, designed to be inserted into the AGP slot on a motherboard to allow for additional dedicated memory for graphics processing. Those motherboards that included onboard memory use a shared graphics memory design versus the dedicated graphics memory found on a removable AGP video card. The graphics acceleration and processing capability on an onboard video card and shared memory is not as powerful. By using the AIMM expansion card, users can gain some improved graphics acceleration and processing capability for less than the cost of an AGP video card.
The AIMM expansion card provided 4 MB of dedicated graphics memory. Motherboards with the capability to utilize the AIMM expansion cards became more readily available in the early 2000s. While more cost effect, the AIMM expansion card was still not as popular a choice as an AGP video card for dedicated graphics memory.
As motherboards with PCI Express became available, computer users switched to PCI Express video cards and the AGP graphics acceleration era faded away, including the AIMM expansion card.