Sometimes it is necessary to reduce the number of
processors on a system for testing, particularly
performance testing. Instead of countless iterations of
testing, shutdown, opening the hardware to remove a CPU,
then putting it all back together, here's a procedure that
makes the Windows NT operating system disable the use of
multiple processors.
Procedure
=========
From the Registry select the following:
HKEY_LOCAL_MACHINE on Local Machine SYSTEM\CurrentControlSet\Control\SessionManager
At this point, find the RegisteredProcessors entry. The
default hexidecimal value displayed represents the maximum
number of processors the operating system will support. On
some SMP systems, this value can be as large as 0x20 (32
decimal) even though hardware configurations today only
accommodate a maximum of four processors.
Double click on the RegisteredProcessors entry to bring up
the DWORD editor. Then change the value to reflect the
number of processors you want enabled in the system. For
example, changing 0x20 to 1 will enable only one processor
in the system. You must reboot in order for the system to
recognize this configuration change.
After rebooting, you can confirm the number of processors
currently enabled from the Control Panel. Select the System
icon and then the Environment tab. The environment variable
NUMBER_OF_PROCESSORS will reflect your change.
This procedure works on all multiprocessor Windows NT
systems.