get-internal-real-time and internal-time-units-per-second

[joofung@iss.nus.sg (Wong Joo Fung)]

Hi:

I'm using (get-internal-real-time) to determine how fast a pen gesture can be
issued.  Even though I'm using MCL to run a simulation of the Finder
interface, the simulation feels very lively -- thanks to the help of a Quadra
700 and 20MB of RAM, that is.   :-)

Right now, I'm a little puzzled about the timing accuracy that I can get from
MCL.  That is, MCL 2.0 tells me that internal-time-units-per-second has the
value of 1000 -- and this seems to imply that (get-internal-real-time) has an
accuracy of up to 1 millisecond.  However, the Mac's time manager is only
updated 60 times a second (or so) -- meaning that all times are only accurate
to about 16 milliseconds.

Is there some wizardary that I've missed?  Ie, is MCL using a more accurate
timing mechanism?

Any pointers would be much appreciated.

Thanks and regards,
JooFung Wong

P.S.  Attached are the relevant documentation information for your easy
reference:

   INTERNAL-TIME-UNITS-PER-SECOND  
   [Constant]
   an integer that is the number of Macintosh Common Lisp internal time
   units per second.

   GET-INTERNAL-REAL-TIME  
   [Function]
   returns an integer representing, in Internal Time format, the amount of
   time since your Macintosh computer has been turned on.