so million thanks for your reply i think i made some mistakes in this topic mac os x tiger is a bit powerpc os later versions adding support for bit powerpc console applications and bit intel processor mac os x leopard is a bit universal os with additional support for bit applications for powerpc and intel processors mac os x snow leopard is the apple's first bit os running only on intel processors retaining support for bit powerpc applications mac os x lion is the last os retaining bit kernel for intel processors before i thought os x tiger also supported bit application for intel processor that is something i made confused but i've also heard aix x support bit application on bit kernel so i think for powerpc architecture that would be a common thing but for intel processor that is quite rare at least as i know only apple had gotten a try for days i also read something on hackintosh on the internet so many hackers crack os x kernel to adapt them onto amd platform even though they might hack the kernels with their patches but i don't believe they would re architecture for the xnu kernel i saw many legacy amd kernels could force hacked kernel sitting on legacy mode applications on long mode but in that environment ia applications would fail to start that might say there might be something different between these two architectures intel and amd i've also heard someone could perfectly host os x on some virtual machines as is known to me none popular platform virtualizing software could cluster virtualize a guest os so that could tell apple did not use vt to implement that trick so that way apple went even further than microsoft's wow in my imagination bit kernel might provide essential os mechanism to host bit applications each time application loader aware of bit application would be ready to run it sets up lot of hooks onto the long mode to ensure bit application would believe they are just sitting in bit os when they requires the system all those bit hooks would grasp the processor from long mode back to legacy mode kernel to the real jobs so in this situation a processor would switch between legacy mode and long mode much more frequently than usual in os x leopard only very few applications such as chess provides bit images so most time the processor might never need to swift to the long mode but in snow leopard if intel processor found at system initialization all applications running within bit mode so in this situation i confused myself whether compatibility mode host the ia applications or the legacy mode host them but i would prefer the latter even though apple ever linked these two architectures ia and intel together so seamlessly but i would differentiate ia with x anyway again thank you very much for your reply