SQL Server 2008 operates in a very different environment than previous versions of SQL Server. When SQL Server 2000 was launched, a large server used for SQL Server may have had four to eight processors. Now SQL Server 2008 is able to run on the largest servers, with 64 cores, and up to 1TB of RAM running Windows Server 2008 or Windows 2003 Datacenter Edition. Currently, there is a bewildering array of processor options to consider when obtaining a new system. SQL Server 2008 can run on a wide variety of processors:
32-bit processors: x86
32-bit with 64-bit extension processors: x64
64-bit processors: IA64
What follows is a short introduction to these different processor families, along with a short discussion of some of the factors that influence making a decision about which processor you should use.
A processor standard for more than a decade, an x86 processor can support up to 32 cores and can directly address 4GB of virtual address space where 2GB is assigned to a Windows process — for example, SQL Server — and 2GB is kept by the operating system. With the 3GB option, it can assign 3GB to a Windows process instead of 2GB. With the Address Windowing Extension (AWE), SQL Server can support up to 64GB. For SQL Server, AWE memory can only be used for data pages caching. Moreover, access to AWE memory is slower than the virtual address memory. 32-bit systems are fast becoming a legacy platform, and have largely been replaced by 64-bit systems. ...