File:Apple HMMU prototype.jpg

A custom daughtercard, functioning as a hardware memory management unit (HMMU), in a prototype Macintosh II, code named "Paris". The daughtercard is occupying the socket of a Motorola 68851 paged memory management unit and contains three Programmable Array Logic (PAL) chips produced by Monolithic Memories, Inc. This was consolidated into the VLSI VI475 HMMU upon release of the Macintosh II to the public.

Source

 * “Paris” Prototype Apple Macintosh II Motherboard by Plocmstart! 2017-04-08.