If the event represents a threshold crossing event, the two
objects hwDot3ahEfmEventWindowHi and hwDot3ahEfmEventWindowLo form an
unsigned 64-bit integer yielding the window over which the
value was measured for the threshold crossing event (for
example, 5, when 11 occurrences happened in 5 seconds while
the threshold was 10). The two objects are combined as:
hwDot3ahEfmEventLogWindow = ((2^32) * hwDot3ahEfmEventLogWindowHi)
+ hwDot3ahEfmEventLogWindowLo
Otherwise, this value is returned as all F's (2^32 - 1) and
adds no useful information.