Download (direct link):
If a quick analysis suggests a closer look, then you can collect and analyze more detailed data on CPU usage with the Performance console. Here are some of the counters to watch:
* Processor\% Processor Time: What percent of total time the CPU is busy doing useful work. Periodically pegging out at 100% is okay, but long stretches over 85% indicate a bottleneck (or a misbehaving application).
* Processor\Interrupts\Sec: How many hardware interrupts the CPU deals with per second. Hardware interrupts come from devices rather than from programs. Microsoft says watch out if you have more than 15 here.
* Processor\% Privileged Time: What percent of the CPU's busy time (or 'non-idle time' as Microsoft puts it) is spent in privileged mode, that is, handling operating system and hardware requests (as opposed to user mode, which applications typically use). If this value goes up suddenly and dramatically, you may have a failing network card or other device; adapters sometimes flood the CPU with interrupts when they go bad.
* System\Processor Queue Length: How many threads are waiting around in line to be handled by the CPU (or CPUs, in a two-processor system). Any number greater than two may mean processor bottleneck.
On a multiple-processor system, you can specify which processor you want to measure by making a selection in the instances list of the Add Counters dialog box. You can specify that you want to measure all processors, in aggregate, by choosing the _Total instance.
You can make a very broad adjustment to modify whether Windows XP pays more CPU attention to the foreground program (the application you're running in an open, active window with a highlighted title bar) or pays equal attention to foreground and background programs (background programs being applications and services that are not running in the top window).
Windows XP Professional defaults to the traditional Windows behavior of favoring the foreground program, but you may prefer a more server-like distribution of processor power if you often run background programs (such as backup or printing operations) and if those programs run poorly. To make such a change, follow the steps in Lab 14-1.
Lab 14-1: Adjusting Processor Behavior
1. Right-click My Computer and choose Properties.
The System control panel appears.
2. Click the Advanced tab.
3. Click the Settings button in the Performance area.
4. Click the Advanced tab.
5. In the Processor Scheduling area, click the Background Services radio button.
6. Click OK and click OK again to close the dialog boxes.
Adding a second processor
Based on monitoring as I discuss earlier in this section, you may find that you need to add processing power to a PC for which the CPU has become a bottleneck. If you run graphics-intensive applications, engineering design software, or scientific analysis programs, then you may be a candidate for CPU turbocharging. You can add processing power two ways: by replacing your CPU with a faster one (assuming the particular PC supports such replacement), or by adding a second CPU to a single-processor machine (again, assuming your PC has the expansion socket available).
Windows XP Professional supports up to two processors in a single PC, using a scheme called symmetric multiprocessing or SMP. If you install Windows XP onto a PC with two processors, the setup program should automatically detect them and install SMP support. However, if you install Windows XP onto a PC with only one CPU installed and then add a second CPU later, Windows XP doesn't automatically detect the change and make adjustments. Adding a second processor fundamentally changes how Windows XP deals with your hardware, and it's not an action that a mere Plug and Play device detection can handle. For one thing, Windows XP uses a different HAL (Hardware Abstraction Layer) for an SMP machine than for a single-CPU machine.
So, the multiple-CPU upgrade requires one of two actions: You can reinstall Windows XP over itself, or you can update the driver for the Computer object in Device Manager. Lab 14-2 details the second method, which usually works fine and which is a lot faster; if it fails, you must reinstall.
Warning The method that I describe in Lab 14-2 may render your PC unusable if you haven't actually installed a second CPU!
Lab 14-2: Reconfiguring for Multiple Processor Support
1. Log in as an Administrator.
2. Run the System control panel by right-clicking My Computer and choosing Properties.
3. Click the Hardware tab.
4. Click the Device Manager button.
5. Double-click the Computer icon at the top of the tree to expand its contents.
6. Right-click your computer model (just under the Computer icon) and choose Update Driver.
7. Click Install From A List Or Specific Location (Advanced).
8. Click Next.
9. Click Don't Choose. I Will Choose The Driver To Install, and click Next.
10. Select the new driver in the Model column, based on your best educated guess.