Advanced Micro Devices Inc (AMD)

[Haddock]

And then, assuming PGI Compilers indeed lower SPEC-scores

I think that's a pretty safe assumption. If you keep the rest of the system constant including the compiler then 64 bit code is faster than 32 bit code on average. See AMD's gcc-based SPEC benchmarks for the 244.

Noone seems to run SPEC as fast as the Intel compiler. That may change (it seems the others are improving faster right now), but right now the others are also-rans in terms of sheer execution speed.

why did IBM use it for Spec reports?

If you are buying an Opteron for high performance (scientific) computing then it could well be in order to run 64 bit Fortran90 code. Gcc can't do that and neither can the Intel compilers (for different reasons), so you have to use PGC.

If you have a particular problem that fits in 32 bits you can use the Intel compiler and get marginally better performance. Note that the Intel compiler is available for Linux too.

If your program is in Fortran77 or C or C++ then you also have the option of using gcc either 32 or 64 bits. Usually the 64 bit version is faster.

There's really no reason to suspect IBM's motives on this one. A lot of their HPC customers will use PGC Fortran - it's a reasonable thing to benchmark.