Macintosh 512K ROM Upgrade: Memory Available

This article has been archived and is no longer updated by Apple.
The upgrade makes a negligable difference of 1.5K in available memory over the
372K available on the original Macintosh 512K. This is the result of the
combination of more system stuff and an increase in the system heap for global

The benefit of the 128K ROMs is in the increased speed in performing rote
functions: opening and closing windows, redrawing, and accessing the faster
ROM-based routines instead of the slow RAM-based routines.

Published Date: Feb 18, 2012