This is the MMU or "Memory Management Unit" for the Atari 8-bit Computer system. All Atari 8-bit computer systems use an MMU and some are getting hard to find. These MMU chips are created from an off-the-shelf ATF16V8B chip which is programmed to function as a replacement MMU.

Like Atari's other XL and XE computers, the Atari 1200XL has a "Memory Management Unit" or MMU. This is reproduction of Atari's 1200XL MMU for which the part number is C060609 and it is installed in socket U14 on the system board.

The 1200XL MMU differs from the "standard" MMU in that the 1200XL has 2 ROM chips. Because of these 2 ROM chips, a slightly different MMU is required in order to handle them.

The first picture shows the chip by itself and the second picture shows the chip installed in the system board of an Atari 1200XL. (Atari 1200XL system board not included, of course.)