I am not apple IIe expert (I was a commodore guy) but:

"In March 1985, Apple replaced the original machine with a new revision called the Enhanced IIe. This change involved a new processor, the CMOS based 65C02 CPU, a new character ROM for the text modes, and two new ROM firmware chips."

http://en.wikipedia.org/wiki/Apple_iie#The_Enhanced_IIe