32- and 64-bit Versions of Windows Server 2008

Several editions of Windows Server 2008 support both 32- and 64-bit processors. In fact, these editions will support both x64 and IA64 processors. IA64 is based on the Itanium microchip from Intel—Itanium is a 64-bit reduced instruction set computer (RISC) processor—and while it is in use in very large organizations, has a very small following.

x64, on the other hand, offers the most important evolution in computing since the release of 32-bit processors. Because of the exponential nature of microchip technology, 64 bits actually offer significantly more processing power than simply doubling the capability of 32 bits. According to Bill Gates, the coming of 64-bit computing will break all the barriers we face today. That may be true. One thing is certain: x64 machines provide a lot more horsepower than x86 machines. x64 systems run a series of different processors from the two microprocessor manufacturers: from AMD, the Opteron or the Athlon 64; and from Intel, the 64-Bit Xeon or the Pentium with EM64T. What’s exciting about these processors is that they are a lot more affordable than the I64 systems. In addition, you have a much larger variety of operating systems to choose from: Windows Vista 64-bit edition, as well as Windows Server 2008 Standard, Enterprise, and Datacenter editions.

There are two ways to work with an x64 system: run native 64-bit software, or run software that is compatible but runs in 32-bit mode. You might think that because the x64 versions of Windows Server and Windows Vista have only been out for a little while that there might not be a lot of applications available for this version of the OS. But that’s not the case. According to the Microsoft Web site (see the Windows Server Catalog of Tested Products at www.windowsservercatalog.com), there are hundreds of applications that run in native x64 mode and more are coming. In addition, several more can run in 32-bit compatible mode.

So how does x64 measure up? The first thing you’ll notice is that everything—yes, everything—runs faster. That is as you would expect, but it is surprising to see that even applications that aren’t designed for the x64 system run faster. Just like the 32-bit version of the operating system, x64 runs a special Windows on Windows (WOW) session that lets 32-bit applications run inside the 64-bit operating system. WOW32 sessions provide better performance than even native 32-bit systems. Why is that? Because of the limitations that x64 finally breaks.

Previously, with a 32-bit system, you needed to use at least Windows Server 2003
Enterprise edition to gain access to more than 4 gigabytes (GB) of random access memory (RAM), then add the /PAE (physical address expansion switch) to the Boot.INI file that controls how the operating system is launched. Although this gave you access to more than 4 GB of RAM, it only fools the system, because a 32-bit machine is limited to a 4-GB address space in the first place. With x64, this limitation changes to 32 GB for Windows Vista and the Standard edition of Window Server, but jumps to 1 terabyte (TB) when running the more advanced editions of the Windows Server operating system. In addition, there is less reliance on the page file for virtual memory expansion in a 64-bit system. This means less disk activity for memory-intensive applications.

These are not the only benefits of x64. It also provides faster input and output (I/O) because it can take advantage of larger data blocks. It provides higher data transfer rates because it can run more concurrent processes. More client connections can be set for a given server, breaking the limits of Transmission Control Protocol/Internet Protocol (TCP/IP) on 32-bit. In fact, Microsoft states that it has been able to vastly reduce the number of servers running Microsoft Update, the Web site providing patch downloads, because each 64-bit server can manage vastly more connections per server. But these file system changes have an impact. For example, your 32-bit third-party backup and restore tool will not work with a 64-bit machine because the file I/O driver is completely different from the 32-bit version.

Not everything works on x64 machines today, while some applications only run on x64 platforms. One good example is Microsoft Exchange Server 2007; it only runs in 64-bit mode. This is exactly the way it was when 32-bit machines were introduced. Costs are not that far off from 32-bit systems, and the advantages are far-reaching.

Source of Information : McGraw Hill Microsoft Windows Server 2008 The Complete Reference