EDITOR'S NOTE
The Buyer's Guide presents vendor-submitted information. Five vendors we contacted about participating in this 64-Bit Dual-Processor Servers Buyer's Guide—Alienware, Aspen Systems, Fujitsu, Verari Systems, and Xi Computer—didn't respond to our requests for information. To find out about future Buyer's Guide topics or to learn how to include your product in an upcoming Buyer's Guide, go to http://www.windowsitpro.com/buyersguide.

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The IT world is entering the 64-bit era of computing. In the past, you might have found 64-bit systems solely in high-end enterprises, but the advent of x64 processors from AMD and Intel—with their ability to run both 32-bit and 64-bit software—has made 64-bit computing a reality for both large and small businesses. The vast majority of server installations use dual-processor systems, so I've limited the scope of this Buyer's Guide to dual-processor 64-bit server systems. The systems included herein represent the next generation of two-way systems.

Processing Power
The 64-bit processor can be extremely beneficial to several types of workloads. Relational databases, business intelligence, and data warehousing are the server applications that will probably derive the largest benefit from the 64-bit platform. Memory is often the gating factor that limits performance for such applications, and the 64-bit platform's ability to support as much as 16TB of RAM provides a substantial increase in headroom over the 4GB limit of 32-bit systems. All the top TPC-C database benchmarks were achieved on 64-bit systems. Terminal Services is another often-overlooked server application that can yield big benefits on the 64-bit platform. Early Microsoft tests proved that you can realize a 75 percent increase in numbers of Terminal Services users by moving to the 64-bit platform.

The primary consideration to keep in mind when comparing 64-bit systems is the CPU itself. The Itanium and x64 are the two primary types of 64-bit processors. Intel is the sole manufacturer of Itanium CPUs. The Itanium provides the highest level of performance and is the choice for ultimate in high-end scalability—but it isn't binary-compatible with today's 32-bit applications. Itanium requires native 64-bit software expressly compiled for the Itanium chip. The Itanium can run 32-bit software but must do so in slower emulation mode. Both AMD and Intel manufacture x64 processors. Although the x64 platform doesn't match the Itanium for ultimate scalability, x64 processors are 100 percent binary-compatible with 32-bit software and can run both 32-bit and 64-bit software at full speed. (In fact, 32-bit applications run slightly faster on 64-bit systems—even in 32-bit mode—simply because of the wider data path.) For x64 servers, AMD makes its line of Opteron processors and Intel makes its line of EM64T XEON processors. (There are also 64-bit x64 processors for desktop and mobile systems. Intel makes its 64-bit Pentium 4 for desktops, whereas AMD manufactures the Athlon 64 for desktops and the Turion for laptops.)

Another important factor to consider in an evaluation of 64-bit systems is the system's maximum supported memory. Increased memory is the primary benefit of moving to the 64-bit platform. However, not all systems provide support for physical RAM that goes beyond the 32-bit levels. At a minimum, you should look for systems that support at least 4GB of RAM.

Other Factors to Consider
Internal expansion capabilities are also essential. Look for the number of supported expansion slots and their type. These slots are typically PCI or PCI Extended (PCI-X). Many newer systems will also have higher-performance PCI Express slots. Older PCI expansion slots are based on a 32-bit bus and run at speeds of 33MHz and 66MHz. The updated 64-bit PCI-X bus jumps past those speeds, supporting 66MHz, 133MHz, 266MHz, and 533MHz bus speeds. The newer PCI Express uses a serial architecture that, in a 1x configuration, supports bidirectional transfers at up to 250MBps.

Don't overlook the disk drives that are included in the system's base configuration. Today, many manufacturers are dropping the floppy-disk drive from the basic configuration. However, Windows still requires a floppy-disk drive for loading drivers during installation. In addition, be sure to pay attention to the included optical drives. Many systems come with a CD-ROM drive but no DVD-ROM drive, and there are several software applications that come on DVD media.

Finally, be sure to take note of the software that's bundled with the system. Many system builders have the option to bundle the OS along with packages of CALs. In addition, several vendors bundle proprietary management tools as well as various other third-party tools.

Rev It Up!
The current crop of 64-bit servers takes performance and scalability to new heights. The x64 systems do so without putting a big dent in your budget or causing application-compatibility problems. But if you're after the ultimate peaks in scalability, the Itanium-based systems offer a significant advantage.