GHC just produced its first working binary on x86-64 :-D $ uname -a Linux amd64-linux1 2.4.19-SMP #1 SMP Thu Jul 17 21:37:10 UTC 2003 x86_64 unknown $ cat hello.hs import System.Info main = print System.Info.arch >> print System.Info.os $ ./ghc-6.0.1/ghc/compiler/stage1/ghc-inplace hello.hs $ file a.out a.out: ELF 64-bit LSB executable, AMD x86-64, version 1 (SYSV), dynamically linked (uses shared libs), not stripped $ ./a.out "x86_64" "linux" $ Unregisterised, no GHCi so far. I had to make precisely two changes to the GHC source code: one to the configure script to recognise this platform, and one to the known hairy bit of the RTS that handles memory allocation (ghc/rts/MBlock.h). The second of these changes *should* go away when I figure out how best to generically handle 64-bit arches in the MBlock code (there's already generic 32-bit support). As a side-effect, I've written a bunch of instructions on cross-compiling GHC for a new platform, which I'll put in the porting section of the Building Guide. Cheers, Simon