On Mon, 19 Jul 2004, Jeremy Mann wrote: > First, do you know if the opteron kernel will allow larger memory for user > space in 64bit mode that just 4 GB? We have two dual Xeon's with 4gb of > memory which we could never get more than 3.5 GB recognized by the 2.4 > kernel. If your user-space app is compiled as a 64-bit binary, it will see >4GB of RAM (or whatever your RAM + swap is). If your app is a 32-bit binary, it will see al the 4GB of RAM it can actually address, but nothing more. However, the 32-bit binaries don't have to share the 4GB address space wih other processes unlike what you're seeing with a 32-bit kernel/machine now. Note that this is assuming you're running a 64-bit kernel of course. Cmpiling 64-bit apps was a bit confusing at first (mixing 32-bit and 64-bit libs during linking, etc.) but we got the hang of it after a while. Someone else will have to answer the power question, I only have a measly half dozen Opterons (a mix of IBM x325 and home-made ones) at the moment. :-)