Conventional software runs in an "emulation" mode, which is functionally similar to the 68020 processor. The main differences between the 68020 processor and later processors are: (a) it does not have a PMMU (Paged Memory Management Unit), ( B) it does not support the SWAP16 instruction, and © it does not support a floating point unit. The first point is necessary because the PowerPC has a newer, better, memory management model. The second point is also addressed by improvements in the PowerPC chip. The third point requires different steps to work around; see the FAQ question below. Conventional software will generally run faster than a 68020, probably between Macintosh IIci and Quadra 605 performance, depending on how many references the software makes to the native "toolbox" in the computer.
