Two CPUs in One?

The latest Pentium 4 chip reaches 3 GHz and promises you a virtual second processor via Intel's hyperthreading technology

Test Center: Notes From the Lab

For optimum single-application performance, you must do more than disable hyperthreading in your new system's BIOS: You must remove the Windows XP multiprocessor files. One way to do this is to turn the PC off and then reinstall Windows XP from scratch. That's because the multithreaded version of Windows XP loads more files and uses more resources than the standard version, and so imposes a performance penalty from the get-go--when you switch off hyperthreading, those files are still loaded.

Adobe Photoshop can show dramatic speed improvements with hyperthreading, but you have to use the right filters, such as Crystallize or Radial Blur--those that tend to do calculations throughout the process instead of just simple conversions. Multiple calculations keep the CPU busy and take advantage of hyperthreading efficiencies. You can get bottlenecks if you have an application--or multiple single-threaded applications--that try to use the same resources on the chip.