Atari MMU is a custom

memory management unit A memory management unit (MMU), sometimes called paged memory management unit (PMMU), is a computer hardware unit having all memory references passed through itself, primarily performing the translation of virtual memory addresses to physical ...

chip for the

Atari 8-bit The Atari 8-bit family is a series of 8-bit home computers introduced by Atari, Inc. in 1979 as the Atari 400 and Atari 800. The series was successively upgraded to Atari 1200XL , Atari 600XL, Atari 800XL, Atari 65XE, Atari 130XE, Atari 800XE, ...

computers. It enables access to the hardware registers on

ANTIC Alphanumeric Television Interface Controller (ANTIC) is an LSI ASIC dedicated to generating 2D computer graphics to be shown on a television screen or computer display. Under the direction of Jay Miner, the chip was designed in 1977-1978 by ...

GTIA Color Television Interface Adaptor (CTIA) and its successor Graphic Television Interface Adaptor (GTIA) are custom chips used in the Atari 8-bit family of computers and in the Atari 5200 home video game console. In these systems, a CTIA or GTIA ch ...

POKEY POKEY, an acronym for Pot Keyboard Integrated Circuit, is a digital I/O chip designed by Doug Neubauer at Atari, Inc. for the Atari 8-bit family of home computers. It was first released with the Atari 400 and Atari 800 in 1979 and is include ...

and 6520 PIA. The later XL/XE MMU (C061618) also selects OS

ROM Rom, or ROM may refer to: Biomechanics and medicine * Risk of mortality, a medical classification to estimate the likelihood of death for a patient * Rupture of membranes, a term used during pregnancy to describe a rupture of the amniotic sac * ...

Atari BASIC Atari BASIC is an interpreter for the BASIC programming language that shipped with the Atari 8-bit family of 6502-based home computers. Unlike most American BASICs of the home computer era, Atari BASIC is not a derivative of Microsoft BASIC a ...

ROM, self-test ROM and LEDs in the 1200XL. On the 128K 130XE the EMMU chip handles similar functionality. The user cannot directly manipulate the Atari MMU, but selects the various ROMS and memory via the memory-mapped hardware register known as PORTB (54017₁₀ or D301₁₆). Atari changed PORTB from an input port on the 400/800 machines to an output port on the XL/XE machines, leaving two joystick ports instead of four on the XL/XE machines. By setting and clearing specific bits in PORTB, the user can access either the ROMs or memory locations. No synchronization is required as the OS handles the access. The bit assignments for PORTB on the XL/XE machines are: Note: The 1200XL does not have BASIC built-in.

References

* Chadwick, Ian (1985). ''Mapping the Atari Revised Edition''. COMPUTE! Publications, Inc.

External links

jindroush site(archived)
MMU info
INSIGHT: Atari - Compute! Magazine
- Talks about Bank Selection in the Atari XL machines. {{compu-hardware-stub Atari 8-bit family, MMU, Atari

See also

References

External links