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102 CHAPTER THREE
The major advantage of a uCoded CISC machine is in the richness of the instruction
set. Many of the CISC machine designers provide specialized instructions that can be
of great use in specific circumstances. Some CISC computers will have specific
instructions for the treatment of continuous streams of data such as might come from
communication interfaces. This becomes almost a crossover capability from DSP
machines. If the robot needs specialized communication or data-processing instruc-
tions, look for them in the CISC instruction set of the processors under consideration.
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Pentium processors have the Multimedia Extensions (MMX) instruction sets and cer-
tain constructs that are good for the processing of vector data.
Some CISC machines provide floating-point instructions, which can greatly speed
up some algorithms. Others provide communication instructions such as the computa-
tion of ECC polynomials and Viterbi codes.

COPROCESSORS
In an effort to provide extra horsepower for their processors, some designers couple
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processors together. The Pentium class processors can operate in tandem. This allows
the same programs to operate a bit faster without significant modifications. For more
information, go to www.intel.com/products/server/processors/server/xeon_mp/index.
htm?iid=search+XeonMP.
Other designers coupled together processors with disparate capabilities. The
PowerPC ™ from Motorola is in such a class. The second processor is termed the
communications processor and is reserved almost exclusively for the use of Motorola
processor designers to provide communication processing. It’s a simple RISC machine
that is not documented for end users. It’s used, for instance, to provide the processing
necessary to implement LAN (local area network) communication interfaces. The com-
munication processor can handle several communication interfaces at the same time,
limited only by the overall bandwidth of the coprocessor. Other communication proto-
cols like ATM, Sonet, and others are available as complete uCode that can be loaded into
the coprocessor and kicked off.
If we can find a processor with significant coprocessing power, it can be used for par-
allel processing. The newly introduced network processors can be used like this. They
are basically multiple RISC processors in a single chip. They’re used for the process-
ing of packets on the Internet, a task that can be partitioned and requires great horse-
power. These chips are available from Vitesse, IBM, Motorola, and many others. Thus
far, they have been used only for network processing, which handles IP packets in real
time, but they are very powerful parallel processing machines and might work well in
a robot control system.