Agnus is the central DMA controller and address generator chip in the Amiga's custom chipset, responsible for managing access to Chip RAM and coordinating data transfers between memory and the other custom chips without CPU intervention. It contains the Blitter and Copper co-processors, handles memory arbitration between the CPU and custom chips, and generates the memory addresses needed for graphics, audio, and disk DMA. Originally released as part of the OCS, it evolved through Fat Agnus and Super Agnus in the ECS chipset to Alice in AGA, with each generation expanding addressable Chip RAM capacity.