PC Gamess/Firefly 64-bit processing documentation

Intel Pentium 4/Core 2-specific version of the PC GAMESS 7.0.1 and above is the mixed mode 32-bit/64-bit program. More precisely, base 32-bit code calls some 64-bit computational kernels for faster processing. The use of 64-bit code is especially important running on Core 2 microarchitecture. We recommend all PC GAMESS/Firefly users running PC GAMESS/Firefly on these processors to use 64-bit OS.

This feature is turned on by default under 64-bit Windows and should be manually activated under 64-bit Linux:

$smp call64=.t. $end

AMD-optimized (jargon: so-called "P2-version") PC GAMESS/Firefly binaries do not support calls to 64-bit code as this does not result in any performance improvements. However, this is only true for older AMD processors. Barcelona/Shanghai core AMD processors (e.g., four-core Opterons and various Phenoms) should use our "P4-version" and are affected by call64 option.

We are currently working on a pure 64-bit version of PC GAMESS/Firefly.

See also:

Last updated: March 18, 2009