hi, i looked around for answers all over so please forgive me if these questions have been answered before. Given that I have a mac xserve with efi32 and osx 10.6.8. of course it runs with a 32 bit kernel. the machine has a 64 bit processor and will run 64 bit apps. Can a 32bit app address more than 4gb of memory? Can a 64bit app address more than 4gb of memory? If I had efi64 in the machine and booted the 64 bit kernel, Can you run 32 bit apps? Are 32 bit apps a bad idea (based on what you know/experienced)? could a 32 bit app address more than 4gb of memory? Do any of the answers above change with 10.7 or 10.8? also on the mac in question, in about this mac, software, some apps listed say intel 64 bit = yes. for those that do not, could they detect the 32 it kernel and run as 32 bit but run as 64 bits when there is a 64 bit kernel? any links to back up the answers are appreciated (i have to show this to someone else). thanks in advance.