Maybe 10.9 will take advantage of more memory? Does anyone know?
Ha HA! From OWC:
**Mac OS X versions prior to 10.9 Mavericks are unable to utilize more then 96GB RAM due to an operating system limitation. 128GB can be fully utilized by a 2009-2010 Mac Pro if running 10.9 Mavericks or later, Bootcamp with 64-bit versions of Windows XP and later as well as with 64-bit versions of Linux.