68EC040, 68LC040, and 68040 Differences

If you have been looking around for 68040-based computers, you may have noticed that there are three different types of 68040 processors. I have long known about the 68LC040 and 68040 versions but the 68EC040 was a new one I had never heard of. The 68LC040 processor has a memory management unit (MMU) but no floating point unit (FPU). The full 68040, the most desirable, has both an MMU and FPU. The 68EC040 which I had never heard of contains neither an MMU or FPU. Macintosh computers have never contained a 68EC040 CPU while both the 68LC040 and full 68040 CPUs have been used.

This might clear up some confusion that some may have regarding these different CPUs. If the purpose of using a 68040-based system is to run NetBSD/mac68k or OpenBSD/mac68k, you really need the full 68040 CPU. There is a NetBSD/mac68k softfloat build available at this ftp site. However, some 68LC040 CPUs have a hardware bug that does not allow floating point emulation to work at all. These CPUs must be replaced in order to function correctly with any NetBSD/mac68k softfloat build. You can read about the details of the hardware bug at this site. Unfortunately, there is no softfloat build available for OpenBSD/mac68k. It is very unlikely that there will be one any time soon.

Information on the Motorola 68040 CPU is available from Wikipedia. You can also look up the 68000, 68020, and 68030 processors. All four of these processors powered 68k Macintosh computers. The final development of the 68k line was the 68060 processor. This final processor of the line was never used in any Macintosh computers. By that time, Apple had moved on to the PowerPC line.