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www.dl.ac.uk/TCSC/disco/Benchmarks/whetstone.html
www.dl.ac.uk/TCSC/disco/Benchmarks/spec.html COMPUTER HARDWARE 117
The following URLs contain some benchmark results:
http://spec.unipv.it/results.html
www.eembc.org/
http://kennedyp.iccom.com/riscscore.htm
http://kennedyp.iccom.com/cpuscore.htm
www.cpuscorecard.com/benchmarks2.htm
www.netlib.org/performance/
So what do we do with all these numbers? We’ve seen how we can get a parametric
evaluation of a processor. If we have done our calculations properly (in the case of cal-
culating MIPS) or if all of our assumptions are correct (about the applicability of bench-
mark data), then we can compare processors directly in terms of compute crunch. The
processor with the best performance can be chosen (all other things being equal).

Arithmetic Capability
Most processors have fixed-point instructions. Some processors have floating-point
™
arithmetic instructions built in. The PowerPC is in this class (see http://developer.
apple.com/techpubs/mac/PPCNumerics/PPCNumerics-146.html).
If the robot must process quantities of floating-point numbers, this capability will be
important. Processors with just fixed-point instructions can still execute floating-point
instructions, but the execution will be much slower than that of a processor with intrin-
sic floating-point instructions.

Word Length

We’ve discussed word length before, but it’s worth listing again. It’s certainly an impor-
tant characteristic of a processor. Processors with longer word lengths generally have
added capabilities that make them much faster than one might expect. A 32-bit proces-
sor is generally much more than 4 times faster than an 8-bit processor.

Memory Size
Many small processors have RAM and ROM memory built right into the processor
chip. It’s easy to get 8-bit processors with such internal memory, and even some 32-bit
processors. If the robot’s control program is very small, and the number of robots to be
built is large, consider these sorts of chips. It’s wise to double all estimates of memory
size; get much more than might be needed. The larger the memory size, the better.