I hope the bogus underflow problem is fixed in CVS Python now. Since my platform didn't have the problem (and still doesn't, of course), we won't know for sure until people try it and report back. Python used to link with -lieee, but somebody changed it for a reason history may have lost. See comments attached to Huaiyu Zhu's bug report for more on that: http://sf.net/tracker/?func=detail&aid=525705&group_id=5470&atid=105470 If someone on a box that had the problem can build current CVS Python with and without -lieee (I'm told it defaults to "without" today, although that appears to mixed up with whether or not __fpu_control is found outside of libieee (search for "ieee" in configure.in)), please try the following in a shell: import math x = 1e200 y = 1/x math.pow(x, 2) # expect OverflowError math.pow(y, 2) # expect 0. pow(x, 2) # expect OverflowError pow(y, 2) # expect 0. x**2 # expect OverflowError y**2 # expect 0. If those all work as annotated on a box that had the problem, please report the success *as a comment to the bug report* (link above). If one or more still fail, likewise please give box details and paste the failures into a comment on the bug report. Thanks!