I have the option of running either the 32 or 64 bit PPS sieve, but if I run the 64 bit version, I need to either keep a CPU core idle or stop crunching on the GPU.
Since I'm not going to shut off the GPU, that means if I run the 64 bit version of the sieve I'll lose about 25% of my CPU crunching power due to the idle core.
Anyone know by how much the 32 bit version is slower than the 64 bit version? Is it worth it to keep a core idle, or should I just crunch in 32 bit mode?
Does this apply to the other sieves as well?
If it makes a difference, the operating systems are 32-bit Vista and 64-bit Unbuntu.