  Today's most popular CPU can operate in two different computational modes for
double precision computations. This fact is not very widely recognized among
scientific computer users. The present paper reports the differences the modes
bring about using the most thoroughly studied system in chaos theory, the
logistic map. Distinct virtual periods due to finite precision come about
depending on the computational modes for the parameter value corresponding to
fully developed chaos. For other chaotic regime various virtual periods emerge
depending on the computational modes and the mathematical expressions of the
map. Differences in the bifurcation diagrams due to the modes and the
expressions are surveyed exhaustively. A quantity to measure those differences
is defined and calculated.
