Few Questions over WPILib Code

[theprgramerdude]

First of all, for the Encoder->GetRate() function, it's return type is a double, but what units does it return it in? Revs/sec, rads/sec? Is there a maximum rate at which this can be called, even though the physical limit at which meaningful data can be obtained might be around 10,000 revs /sec max?

Second, for the Timer functions, is it possible to obtain microsecond or better accuracy by subtracting two different timestamp functions, like GetPPCTimeStamp() or GetFPGATimeStamp(), and furthermore, are these timestamps just representations of how many clock cycles have passed, and thus dependent on the speed of the proccesor, or of the actual time in seconds passed?