Preface: My background is mostly windows environments, so I may be missing something obvious.
On my OS X 10.6 machine when I have 64-bit Kernel and Extensions turned off (which I gather is the default), my computer currently reports 5 GB of RAM in the following configuration:
DIMM 1: 1 GB DIMM 2: 2 GB DIMM 3: 1 GB DIMM 4: 1 GB
When I enable the 64-bit Kernel and Extensions by rebooting and holding down the '6' and '4' keys, it report 3 GB of RAM in the following configuration:
DIMM 1: 1 GB DIMM 2: 2 GB DIMM 3: 0 GB DIMM 4: 0 GB
Does anyone have any insight into what's going on? How can I get my machine to recognize all the RAM? Is this a hardware problem? It seems unlikely.