ls, I always used the /3GB and /userva=3030 switch on Exchange 2003 enterprise with 4GB of memory. Now I have 16GB of memory should I add the /PAE option also to gain performance ? (hardware used is BL480C) Regards Peter

In this KB article http://support.microsoft.com/kb/912376/en-us Microsoft recommend do not install more than 4GB of physcial ram in Exchange 2003. Exchange Server will not take advantage of additional RAM even if it is available

Thanks for the quick reply, Should the parameter /pae be used in the boot.ini when 4GB of memory is installed ? Regards Peter

In another kb http://support.microsoft.com/kb/827281/en-usto point out Memory scalability Because Exchange Server uses the /3GB switch as it scales up, the Exchange Server computer cannot efficiently use more than 4 gigabyte (GB) of RAM. Exchange Server does not support instancing, Physical Address Extension (PAE), or Address Windowing Extensions (AWE). Therefore, 4 GB of RAM is the maximum amount of memory that an Exchange Server computer can efficiently use.