Seems there is a lot of confusion about the different 64 bit architectures and which are supported for SQL Server 2005 to run on. And the different vendor acronyms to describe the architectures just add to the confusion.

Here is a brief note trying to sort this out.

There are only two 64 bit architectures supported by SQL Server (and actually driven by the supported 64-bit architectures for Windows). The separation is based on the underlying processor architecture.

The first one is IA-64 (or Itanium) and it is based on the EPIC (Explicitly Parallel Instruction Computing) instruction set. This is Intel’s first true 64-bit chip.

The second 64 bit architecture is x64 (or x86-64) which is essentially the x86 architecture with extensions to include 64 bit functionality. All Intel x64 and AMD64 processors fall in this category. It was first introduced with AMD’s Athlon 64.

There is no 32 bit equivalent for IA-64 as it was designed to be 64 bit from the beginning.

It is more correct to say x86-32 for the 32-bit equivalent, as x86 is the generic name for the architecture which started with Intel’s 8086 processor which was 16-bit. The x86-32 was introduced with the Intel 386 processor.

More details on 64-bit computing with SQL Server 2005 are available here:
http://www.microsoft.com/sql/editions/64bit/overview.mspx