Just wondering if there is much if any improvement in switching to 64-bit windows-xp or win7-64 over winxp32

The same binary will be used, so if the current workunits are running well for you there will be no improvement. However, if you are having malloc errors for the larger workunits even though you have 1.25-1.5 GB/core, Windows 7 does a better job allocating large amounts of memory so those errors may go away.

Greg,

Thanks for the response, I know for some applications 64-bit is faster than 32-bit, just wasn't sure if it applied here. Worth the upgrade etc...

Basically I'm running NFS bionic b/c of the OP comment, I have enough memory when running 3 apps of psp and a 16 nfs, I have 2 GB dedicated to NFS. If there were a OPN specific for NFS I might try to run 2 cores at 3GB of memory and upgrade to 64-bit.

Is there any thoughs of making a OPN specific preference?

I generally concentrate on Cunningham composites, which only occasionally overlap with the OPN project such as the recent 3,563-. However, 3,607- was such a perfect match for my goals and a most wanted OPN number, so I decided to do it even though at the time it was not a Cunningham number. It has since been added to the Cunningham tables.