In contrast with Motorola's CPUs, the IBM PC clones use processors (or compatible processors) from Intel, the 80x86 family. Intel kept compatibility with the 8088 - their 8-bit processor - and every processor they have made since has to include special options to work around this "bottle neck", including emulation modes and all manner of tricks.
The 80486 is a fast processor - but it could have been so much better. In particular, memory addressing techniques on the Intel family are bizarre - and nothing like the simple sequential one-address, one memory location system used by Motorola.
The Intel Pentium chip has been around for a while. These days it is extremely advanced and there will be many follow ups. The latest Motorola chip, the 68060 (the 68050 was scrapped) runs much faster than a 68040, and also a lot cooler. However, the 68060 will be the last of the 680x0 family as Motorola move into PowerPC processors.
Back to Motorola - The Microprocessor
A.T.Pon@cs.cf.ac.uk