How is the cpdn client built for the different platforms? Is it compiled from a single source tree, or do you use slightly modified and ported versions for Windows, Mac and Linux. Do you use the same compiler on all platform (maybe gcc)? It is probably not easy to get a fortran app of this size working on three different OSs or compilers.

>>It is probably not easy to get a fortran app of this size working on three
>>different OSs or compilers.

Tell me about it! ;-)
We use Intel Fortran compilers on Windows & Linux, although they have vastly different options for each. On Windows we use Visual Studio 2003 (.NET) which is compatible with the Berkeley BOINC code as well as the Intel Fortran for Windows 8.0. On Linux it's Intel 8.0 for Linux and Mac is IBM XLF Fortran (distributed by Absoft). The Mac was the hardest since choice of Fortran compiler is limited. The code is a not-always-standard Fortran 90 so gcc was not an option.

The Fortran codebase (the UK Met Office model) is about a million lines of code (40 megabytes of source code), written by hundreds of scientists over decades, so it's not very possible to dig in and split into "SETI-sized" workunits etc. I compare it to the complexity of compiling a Linux kernel with a lot of device drivers and sending it around the world on different computers to run!

What about PGI and Pathscale for the upcoming AMD64 version? Is it compatible, maybe one of them want to sponsor CP with a free compiler suite?!

Carl, I wonder have you upgraded to 8.1 Intel compiler? Do you use -fast option? -fast option includes interprocedual analisys and sometimes can boost performace significantly. http://www.intel.com/software/products/compilers/cwin/whatsnew.htm
Do you use profiling? Profiling gives 10-15% better performance on average scientific application.
By the way 8.1 compiler supports amd64.