This is almost certainly a dupe, but I don't have a record of it:
I built on mac os x 10.4.6 and got warnings about the heartbeat frequency, e.g.,
./mix > test6.out 1.374983 secs elapsed cpu time heartbeat frequency = 48.72787518100223 Hz *** possible problem: expected heartbeat frequency = 100. Hz
Reporting, as a just-in-case.
Brian