The application must be running on a 64bit OS and in native 64bit mode to gain the advantages of x64, unsurprisingly. If you're running in 32bit mode, either on a 32bit OS (with a 32bit app), you will get 32bit atomicity. If you're running 64bit mode on a 64bit OS on a 64bit CPU, you will get 64bit atomicity. All of the components in the chain (app, OS, CPU) must be running 64bit to get 64bit.
↧