The Kickstart ROM is not a custom chip but a mask-programmed ROM chip for most versions. It contains the largest part of the operating system. Kickstart 1.x ROMs have a capacity of 256 KiB, Kickstart 2.x and 3.x contain 512 KiB. 32-bit Amigas use a pair of 16-bit chips to provide full-width access. Later, non mass-produced upgrade versions were often realized with PROMs or EPROMs.
