This article is from the Macintosh system software FAQ, by Elliotte Harold email@example.com with numerous contributions by others.
MODE32 and the 32-bit enabler are system extensions that allow
Mac II's, IIx's, IIcx's, and SE/30's to access more than eight
megabytes of real memory under System 7. The 32-bit enabler is buggy
and doesn't work at all with System 7.0 or 7.5. If you have more
than eight megabytes of real memory in an SE/30, II, IIcx, or IIx,
(or eight megabytes and RAM Doubler) you need MODE32. See