CurrentControlSet\Control Subkeys

This subkey contains parameters that control system startup, such as subsystems to load, the size and location of paging files, and so on.

Note The system must be restarted for any changes in the Control subkey to take effect.

The Control subkey itself can contain the following value entries:

Current User REG_SZ Username

Specifies the username for the currently logged-on user.

Default: Username

RegistrySizeLimit REG_DWORD 4 bytes to unlimited

Limits both the amount of paged pool the Registry may use, and the amount of disk space.

If the value of RegistrySizeLimit is less than 4 MB, it will be forced up to 4 MB. If it is greater than about 80% of the size of PagedPoolSize, it will be set down to 80% of the size of PagedPoolSize. (It is assumed that PagedPoolSize will always be bigger than 5 MB.)

RegistrySizeLimit sets a maximum, not an allocation, meaning a large RegistrySizeLimit value will be used only if it is actually needed by the Registry. It does not guarantee that much space will be available for use in the Registry.

Setting RegistrySizeLimit to 0xffffffff will effectively set it to be as large as PagedPoolSize allows (80% of PagedPoolSize). PagedPoolSize can be set to a maximum of 128 MB, thus limiting RegistrySizeLimit to 102 MB.

Default: 8 MB (That is, 25 percent of the default PagedPoolSize.)

SystemStartOptions REG_SZ String

Contains the text of system arguments passed to the system by the firmware. These values can be used to determine whether the debugger is enabled, the options set for ports and speed, and so on. For example, the following value could be defined for SystemStartOptions:

   c:\winnt="Windows NT" /DebugPort=com1 /DebugBaudRate=56000

In this example, "Windows NT" in the first part of the string indicates the SystemRoot specified under the Windows NT\CurrentVersion subkey in the Software area of the Registry. The remaining portion of this string is interpreted by the system to define the COM port and baud rate for debugging.

The following standard Control subkeys are found under this Registry path:

   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control

1 These keys contain information used only by the system and should not be edited by users. Because these entries should be maintained only by the system, they are not described here.

2 See "Registry Entries for Printing," later in this chapter.