Microsoft made a series of significant announcements this week at Microsoft IT Forum 2005 in Barcelona, Spain. If you still think of IT Forum as a sort of TechEd Junior, the scope of Microsoft's announcements will help change that perception. The news is that Microsoft is going 64-bit in a big way: the next version of Exchange Server (code-named Exchange 12), the next version of Small Business Server (SBS--code-named Small Business Server Longhorn), and Longhorn Server will all be 64-bit only.

A few weeks ago, I asked for your views about x64 technology. I got some excellent feedback and a lot of questions. This week and next, I'll answer those questions and tell you as much I know about Microsoft's plans for x64 support.

Keep in mind that "x64" refers to a set of processor extensions to the familiar x86 instruction set. Two sets of these extensions exist: AMD calls its extensions x64, and Intel calls its extensions EM64T. Both are distinct from Intel's Itanium processor, which no Exchange versions will support.

Why is Microsoft placing such emphasis on x64? I spoke with Samm DiStasio, director of product management in the Windows Server division at Microsoft, and his take on it is simple. Customers are already buying x64 hardware, and x64 offers major benefits in three key areas: security, scalability, and performance.

x64 offers two security improvements. First is an enhanced version of the data execution prevention (DEP) capability, which prevents malicious code that depends on buffer overflow attacks from working. Data in memory is tagged as such, and the processor refuses to execute anything tagged as data. The other new technology, PatchGuard, is more interesting. PatchGuard prevents user-mode programs from patching kernel routines. Malware authors use this common tactic, particularly in rootkits--leading me to think about naming this column "Windows x64 Kills Sony's Rootkit." (For more information about Sony's rootkit, see Windows IT Pro author Mark Russinovich's Sysinternals blog at http://list.windowsitpro.com/t?ctl=19E0B:10344 .)

The scalability and performance advantages derive from the vastly increased address space that x64 supports, coupled with the fact that native instructions can move twice as much data with each instruction. Microsoft SQL Server 2005, which already has a 64-bit version, has posted some eye-popping Transaction Processing Performance Council (TPC) TPC/C benchmark numbers, and SQL Server customers are eagerly snapping up x64 hardware at a rapid clip.

To ease the transition to x64, Microsoft has done something unusual: The 32- and 64-bit versions of Windows are more or less interchangeable. The x64 versions of Windows have no cost premiums, so OEMs are offering them at the same cost as 32-bit versions. From April 15 through July 30, 32-bit customers could move to x64 Windows at no extra cost. However, now only Volume Licensing customers can switch a 32-bit installation for an x64 installation at no extra cost. I hope in light of the big push towards x64 that Microsoft considers offering another open period when customers who are moving to Exchange 12 can switch OS platforms for no additional cost.

Of course, x64 support requires 64-bit-aware drivers and applications. Driver support is a bigger issue for desktop systems than for servers, but not every vendor of server-related equipment-- including NICs, SAN host bus adapters (HBAs), and so on--has 64-bit drivers yet. In addition, not all applications can run on 64-bit Windows; for example, SAP and Oracle are limited to 32-bit Windows. Applications that don't require kernel-mode drivers can run on x64 Windows in a 32-bit compatibility mode, which makes perfect sense when you think about it.

From an Exchange perspective, of course, the big news is that Exchange 12 will run only on 64-bit Windows. Next week, I'll talk about why Microsoft made this decision and what it means to you.