The Windows Server operating system running in full 64-bit mode on Intel or AMD x86 processors is known as 64-bit Windows Server. Most instances of Windows Server ran in 32-bit mode, even if hosted on a machine whose hardware supported 64-bit mode, up until Windows Server 2008 R2 began shipping. From that point forward, Windows Server will only operate in 64-bit mode, and all new installations are, therefore, 64-bit.