The 64 Bit Question

By now, most of you have heard of 64 bit computers, even if you do not have one. And some of you may even have one and not know it, because you're not running a 64 bit operating system. 64 bit processors are actually nothing new; 64 bit RISC CPUs have been in use since the 1990s, but they were used primarily for servers and very high end workstations. And you might be surprised to learn that IBM and Cray supercomputers of the 1960s and 1970s were based on 64 bit architecture. Only more recently, however, has the technology trickled down to the rest of us.

The more mature among us may remember the transition from the 16 bit Intel 8086 and 80286 processors to the 32 bit 80386 in the mid-1980s. If you are really getting up in years, you might even remember the 8 bit 8080 model that was used in game consoles and the early home computers in the late 1970s and early 1980s. But what do these numbers mean, anyway?

As you probably know, a bit is one binary digit (a 1 or 0). As an aside, in the standard x86 32 bit architecture, a group of 4 bits is called a nibble, a group of 8 bits is a byte, a group of 16 bits is a word, and a group of 32 bits is a double word or dword (now you know what that "DWORD Value" refers to in the registry editor). In the context of this article, the number of bits refers to the amount of data that a CPU can access in a single operation.

When you double the number of bits that can be accessed in a single operation, you make it possible for a computer to process information more quickly. This also affects the total amount of system memory (RAM) that a computer can reference. 32 bit machines can reference 232 (two to the thirty-second power) addresses, which is equal to 4 GB of RAM. That's the reason you're limited to that amount of memory on a 32 bit computer.

With a 64 bit operating system, larger amounts of RAM can be used to full advantage. In fact, the theoretical limit is 264, which is roughly equal to 16 exabytes. What's an exabyte? It's 16.8 million terabytes or 17.2 billion gigabytes - a huge number.

Both the 64 bit hardware and the 64 bit operating systems available today place a lower, artificial restriction on the amount of RAM that will be recognized. The 64 bit version of Vista Home Basic supports up to 8 GB, 64 bit XP Pro and Vista Home Premium both support 16 GB and Vista Business, Enterprise and Ultimate editions support 128 GB.

But even if your hardware supports 64 bits, you cannot take advantage of it or enjoy those higher RAM limits unless your operating system also supports 64 bits. Most computers sold today have 64 bit hardware, but many of them are running 32 bit operating systems. Windows XP Professional and all editions of Windows Vista except the Starter Edition (which is sold only in "emerging markets" outside the U.S.) come in both 32 and 64 bit versions. Vista Ultimate includes both versions in the box.

Just about everyone agrees that 64 bit architecture is the future of computing. On the server side, with some applications you have no choice. For example, the production version of Exchange Server 2007, the R2 of Office Communications Server (OCS) 2007 and Microsoft's Hyper-V virtualization platform are all 64 bit only.

It makes sense for server applications that require large amounts of memory. Hyper-V, for instance, needs to be able to allocate sufficient memory to multiple virtual machines, OCS has to process real-time audio and video streams, and Exchange is a memory-intensive application. Of course, some of us push the memory limits of our workstations, too. On my 32 bit Vista Ultimate computer with 4 GB, RAM usage typically stays in the 65% to 75% range if I have a few browser windows, Outlook, and Word open. In fact, RAM usage is over 50% when I first boot up, before I explicitly open any programs.

Vista is known to be memory-hungry, especially if you use its features to their fullest. If you're like me, you may also have lots of programs that load at startup and run in the background. For instance, I run Orb (for connecting to my computer remotely to access recorded TV and music through Media Center), MOE (the Mesh Operating Environment for connecting my various devices for easy synchronization), Groove Monitor (for using Microsoft's office collaboration system) and others at startup.

You can see what processes are using your memory by opening Task Manager (right click the task bar and select it, then click the Processes tab). Click the column labeled "Memory (Private Working Set)" to arrange the processes in order of their RAM usage. On my Vista workstation, Windows Sidebar is using 80,844 K (I do have a large number of gadgets). Vista Media Center, on which I'm watching a recorded program, is using 72,704 K, Outlook is using 35,716, the Desktop Window Manager (dwm.exe), which is responsible for the 3D effects, window transparencies and other graphical effects in Aero.

If you're using Internet Explorer 8 or Google Chrome, you might notice that you have several instances of those processes (iexplore.exe and chrome.exe), each taking up a chunk of memory. The way these browsers are able to provide better stability and prevent crashing the entire browser when one web site has a problem is by using tab isolation, which opens each tab in its own separate process. The tradeoff is that it takes more memory to run tabs separately.

source: http://www.vistanews.com/