Choosing between Vista x86 32 bit or x64 64 bit

One of the more common questions I hear about Vista is which bit version of Windows Vista should one get.  Do we go with x86 32 bit edition or x64 64 bit edition?  I’m going to try to clear that question up as best as I can and explain the pros and cons of each choice.

First we must understand a little background on what x64 is.  X64 is the 64 bit extension technology that AMD invented (AMD64) to seamlessly migrate the 32 bit x86 (as in 286, 386, 486 compatible microprocessors) world into a 64 bit era.  Intel in partnership with HP had refused to extend the ancient x86 platform and had already committed to its all new pure 64 bit IA-64 Itanium architecture.  While Itanium was fundamentally superior, its x86 emulation provided inferior performance for existing applications and the adoption rate was very slow.  Intel had hoped that the market would leap to the new platform but there was no seamless way of making that migration, and Itanium failed to gain widespread adoption.  AMD took the opportunity to extend the existing x86 architecture with 64 bit capability by handling 64 bit CPU registers and adding a lot more registers, and it was immediately greeted warmly by the market.  In a reversal of roles, Intel found itself copying AMD64 (permitted by an AMD-Intel cross-licensing agreement) and calling it EM64T.  The two x64 technologies are essentially identical except for a few minor differences in the implementation.

Microsoft initially created a version of Windows XP called XP 64 bit Edition, a pure 64 bit operating system that ran on IA-64 Itanium and only supported x86 applications through emulation.  There was even a Windows 2000 Server version for IA-64 as well.  The problem was that the adoption rate of IA-64 was very slow, and when AMD created AMD64–with Intel having no choice but to follow–Microsoft created the x64 edition of Windows XP as well as Windows Server 2003.  The x64 editions were hybrid 32/64 bit operating systems that could natively run 32 or 64 bit code at full speeds without software emulation, whereas the 64 bit edition of Windows XP relied on software emulation to run existing x86 32 bit code.  With the release of Vista, Microsoft simultaneously launched the 32 bit x86 and the 64 bit x64 editions.  The retail editions contain both the x86 and x64 editions, while the OEM versions contain one or the other and you have to decide before you order.  Now one of the most common questions people ask is whether to run 32 or 64 bit Vista.

The first thing you must do is to make sure your particular CPU supports x64. [Dave Leigh in the talkback posted this link to Steve Gibson’s x64 detector which is a simple utility to check your hardware.] Here’s a simplified summary of the situation:

  • Almost all new servers sold within the last two years from AMD or Intel will have x64 capability.
  • Most mid- to high-end desktop processors from AMD or Intel within the last year have x64 capability.
  • Some higher-end Semprons have x64; lower-end Semprons do not.
  • No AMD Durons have x64.
  • All AMD Opteron processors have x64.
  • All AMD X2, FX, and Athlon64 chips have x64.
  • All Intel Pentium D and Celeron D chips have x64.
  • All AMD Turion notebook processors have x64.
  • All Intel Core 2 processors (mobile, desktop, and server) have x64.
  • No Intel Core Duo notebook processors have x64
  • No Intel Pentium M notebook processors have x64.

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