In-Depth

How Does X64 Measure Up?

What works on 64 bits will always work faster, but early adopters will have to accept some limitations. Danielle Ruest and Nelson Ruest put X64 through its paces.

p>64-bit computing. According to Bill Gates, the coming of 64-bit computing will break all the barriers we face today. Perhaps we're dating ourselves, but we remember him saying something of the sort when 32-bit computing started a few years ago. We even remember when we moved from 8-bit to 16-bit processing. Each time, we had new processing power, and bigger and better limits were broken. As you would expect, this is the case with 64-bit machines.

64-bit computing isn't new. In fact, it has been around for some time in the form of Itanium processors. Itanium is a 64-bit reduced instruction set computer (RISC) processor. Microsoft has written a special version of Windows for this processor: Windows Server 2003 for Itanium-based Systems.This version, available in both Enterprise and Datacenter editions, was released in April 2003 but few systems are using it. I64 is a special platform geared toward high-powered systems that must provide the best in processing power. Most I64 systems running today operate critical databases that require the comprehensive processing power of a RISC architecture.

The reason that there is more hype about 64-bit today is the release of X64 systems running Windows. These machines 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 XP Professional 64-bit Edition, as well as Windows Server 2003 Standard, Enterprise, and Datacenter Editions. According to Microsoft, mainstream X64 systems are much more oriented toward everyday computing needs.

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 version of Windows Server has only been out since April 2005, 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, more than 155 applications run or will soon run in native X64 mode. In addition, another 133 can run in 32-bit compatible mode. That's quite of bit of support, especially this early in the game.

Running X64 Through the Paces
OK, 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. WOW sessions provide better performance than even native 32-bit systems. Why is that? Because of the limitations that X64 finally breaks (see Table 1).

That's right. Today, with a 32-bit system, you need to first use at least Windows Server 2003 Enterprise Edition to gain access to more than 4 GB of RAM, then add the /PAE or physical address expansion switch to the Boot.INI file that controls how the operating system is launched. Although this does give 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 XP and the Standard Edition of Window Server, but jumps to 1 TB when running the more advanced editions of the Server operating system. This alone will provide a major improvement. 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 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 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. Backup vendors are working hard to modify their software in support of X64. Some already have working products. Besides, the operating system also has its own version of a backup tool. It's not a Cadillac, but it does work.

The performance of the system will greatly depend on the hardware you acquire. Our test system was a Dell 2800 with Xeon processor and 6 GB of RAM (see Table 2). Performance improvements when compared to a similar 32-bit Dell server were fairly considerable. Our biggest application is the execution of virtual machines. Loading a 64-bit version of Microsoft Virtual Server and running multiple virtual machines was significantly better than on any other system we tested. The operating system worked without a single issue, except that not all 32-bit applications work on this environment.

That's really the gist of it. Not everything works on X64 machines today. This is exactly the way it was when 32-bit machines were introduced. One thing is certain: What does work on 64 bits will always work faster. But early adopters will have to accept current limitations. On the other hand, they'll get to learn and become familiar with 64-bit systems. This means that early adopters will have experience with these machines when the mainstream software is ready to support the OS. Our advice: If you need speed and you know that your core applications are ready to run on X64, take the plunge. Costs are not that far off from 32-bit systems, and the advantages are far-reaching. If you're buying hardware today and you want to make it last, buy X64 machines.

About the Author

Danielle Ruest and Nelson Ruest, both Microsoft MVPs, are IT professionals focused on technologies futures. They are authors of multiple books, including "Microsoft Windows Server 2008: The Complete Reference" (McGraw-Hill Osborne Media, 2008), which focuses on building virtual workloads with Microsoft's new OS.

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