Hi, I recently installed ghc-6.8.3 on an iBook running OS X 10.4.11 (PowerPC G4), using the following distribution: http://www.haskell.org/ghc/dist/6.8.3/maeder/ghc-6.8.3-powerpc-apple-darwin.... Running the following program, compiled with -O, causes an illegal instruction error: =========== module Main where main = print foo foo :: Integer foo = gcd 400 85 ================== Running through gdb produced the following output: Program received signal EXC_BAD_INSTRUCTION, Illegal instruction/operand. 0x00046b50 in __gmpn_gcd_1 () (gdb) where #0 0x00046b50 in __gmpn_gcd_1 () #1 0x00028cb0 in gcdIntzh_fast () #2 0x0002be34 in scheduleWaitThread () #3 0x0001fdb8 in real_main () #4 0x0001fec0 in main () (gdb) quit Christian, did you compile this distribution on a G5 PowerPC? GMP is statically linked into this distribution, so if it's using any processor-specific instructions I could see that tripping up my G4. If you or someone else can confirm that this works on a G5, then we should probably just update the downloads page with that requirement. Thanks, -Judah