GCC now ships with the LGPL-licensed libquadmath library, which provides for targets with a __float128 datatype quad-precision mathematical functions. __float128 is available for targets on 32-bit x86, x86-64 and Itanium architectures. The libquadmath library is automatically built on such targets when building the Fortran compiler.

http://gcc.gnu.org/gcc-4.6/changes.html#libquadmath http://gcc.gnu.org/onlinedocs/libquadmath/ Looks like this is something that actually works. GCC-4.6 is probably about two months away from a release, but this should be functional now. Perhaps it should be supported by petsc-3.2?