Interval regression test failing with -march=pentium4

I'm compiling postgresql 8.1.3 with these gcc flags: -march=pentium4 -O3

The compilation ends correctly but the interval regression test fails.
This is the diff file:

=====================================================================

*** ./expected/interval.out     Thu Mar 23 15:38:42 2006
--- ./results/interval.out      Thu Mar 23 16:16:06 2006
***************
*** 218,224 ****
  select avg(f1) from interval_tbl;
                         avg
  -------------------------------------------------
!  @ 4 years 1 mon 9 days 28 hours 18 mins 23 secs
  (1 row)

  -- test long interval input
--- 218,224 ----
  select avg(f1) from interval_tbl;
                         avg
  -------------------------------------------------
!  @ 4 years 1 mon 10 days 4 hours 18 mins 23 secs
  (1 row)

  -- test long interval input

======================================================================


If i compile the -march=i586 the regression test reports no problems.
Any tips?

Thank you,

Doct. Eng. Denis Gasparin
-----------
Edistar Srl