[Chimera-users] Mac 64-bit Chimera for large data sets

Tom Goddard goddard at cgl.ucsf.edu
Tue Feb 2 12:38:14 PST 2010

A 64-bit Mac Chimera daily build is now available for Mac OS 10.6.  It 
will not run on Mac OS 10.5.


If you work with EM maps larger than 1 Gbyte or molecular models of 
several hundred thousand atoms the larger addressable memory in the 
64-bit version will help avoid out-of-memory errors and crashes.  The 
32-bit Mac Chimera versions can only address 4 Gbytes of memory and 
because libraries, stack and other uses of memory the practical working 
data size limit for 32-bit versions of Chimera is about 1 Gbyte.  You 
should have more than 4 Gbytes of memory installed in order to benefit 
from the 64-bit version.

The 64-bit Mac Chimera is in early testing so will have more bugs than 

I've tested the 64-bit Mac Chimera running Gaussian filtering on a 2048 
by 2048 by 800 map requiring about 3.2 Gbytes for the floating point 
result and 0.8 Gbytes for the original map.  This worked correctly (took 
about 3 minutes on a machine with 6 Gbytes of memory) but failed with 
32-bit Mac Chimera.

We are also working on a 64-bit Windows Chimera that will work with 
Windows 7.  This may be available within a month if no serious obstacles 
are encountered.

A 64-bit Linux Chimera has been available for a few years.


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