active or not. The only sane thing we can do here is assume that if
APM is supported it might be active at some point, and bail.
In reality, even this isn't good enough; regardless of whether we support
APM or not, the system may well futz with the CPU's clock speed and throw
the TSC off. We need to stop using it for timekeeping except under
controlled circumstances. Curse the lack of a dependable high-resolution
timer.
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