All computers contain a chip called a microprocessor, or CPU,
which is responsible for controlling the computer's actions.
Macintoshes have used Motorola's 68000, 68020, 68030, 68040, and
PowerPC microprocessors. Many programs (for example, Dark Forces)
were designed for at least the top-of-the-line chip in the 68000
family (the 68040) to take advantage of the powerful new features
which it provides. Unfortunately, this prevents users of '020 and
'030 Macs from using the software.
Pseud040 is a shareware program for users of 68020 and 68030 Macs
which installs a "virtual 68040" and allows them to run software
which otherwise would require a 68040.