On Thursday, September 01, 2011 11:02:50 am Ed Pozharski wrote:
> I am almost sure this has been addressed before, so you can go after me
> for insufficient googling. However,
>
> 1. Is there any *significant* advantage in using 64-bit CCP4 binaries
> (primarily speed)?
> 2. IIUC, the standard CCP4 download results in 32-bit binaries being
> run on a 64-bit system. Works for me (except for the weird iMosflm
> issue), but given that 64-bit OS is becoming more and more common, isn't
> it time for 64-bit binaries option? The answer, of course, is no if you
> answered no to 1 above.
The generic answer is that there is no intrinsic speed advantage to running
a 64-bit binary rather than a 32-bit binary. In fact it may run slower
due to larger pointer sizes and hence poorer cache performance.
However, 32-bit binaries cannot access more than 4GB of address space.
But the x64 architecture provides more registers and faster instructions
than x86. So a 32-bit binary using the x64 instruction set can run faster
than a 32-bit binary using only x86 instructions. Therefore you need to
choose the right compiler options in order to get the benefit of the faster
architecture.
I do not know if there are specific CCP4 programs that fall outside of
the generic case described above.
Ethan
--
Ethan A Merritt
Biomolecular Structure Center, K-428 Health Sciences Bldg
University of Washington, Seattle 98195-7742
