CPU of the Day: Motorola XC88110 88000 RISC Processor

MC88100 20MHz – 1992

In the late 1980’s Motorola was developing a full 32-bit RISC processor from the ground up.  Initially called the 78000, it was renamed the 88000.  The first implementation of the 88000 Instruction Set Architecture was the 88100.  It included a FPU and integer unit but required a separate chip (the 88200 CMMU) for caching and memory management.  Typically 2 of the 88200s were required (one for instruction cache, one for data, 16kb of cache each).  A 64lb cache was also available called the 88204.  Made on a 1.5u process the 88100 contained 165,000 transistors while the CMMU chips contained 750,000.  Each chip dissipated 1.5Watts at 25MHz.  Prices in 1989 were $494 for the CPU and $619 each for the CMMUs.  A complete system of 3 chips would be nearly $2000.  Not exactly competitive pricing.

The initial, and biggest, customers for the 88000 were to be Apple, and Ford Motor Company, an unusual combination to say the least.  Apple invested in the 88000 to be the replacement for the 680×0 processors it had been using.  Ford was looking to replace the Intel 8061 processors (from which the MCS-96 MCUs were developed) that had run their EEC-IV engine computers since the early 1980’s.  Motorola (as well as Toshiba) had been second sourcing these for Ford for sometime.  Ford based its choice on the 88100 based ECU on the assumption that Apples adoption of the 88100 would guarantee good software and compiler support. If Apple stuck with it that is..

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