vSphere 6.5 was the final release that supports binary translation (BT) mode virtualization of operating systems. VMware virtualization technology, introduced in 1998, was founded on a combination of binary translation and direct execution techniques. These software techniques have since been migrated to hardware and are therefore no longer required. In most cases, this will not affect virtual machine performance when you migrate to future vSphere releases, except in some rare instances where old guest operating systems are still being used. For more information, see KB 2147608.