How To Obtain the Checked Build of the Latest Windows NT 4.0 Service Pack

Checked binaries provide error checking, argument verification, and system debugging code not present in the free binaries.

Much of the additional code in the checked binaries is in the form of ASSERT macros that test an expression. If the expression evaluates to FALSE, the macro generates a kernel debugger error message and breaks into the debugger. This lets you immediately determine the cause and location of the error.

Use the free and checked builds of Windows NT as follows:

• Use the free build on the host machine, running WinDbg.
• Use the free build to develop and build a driver. Performance suffers in the checked build due to the additional code that is executed.
• Use the checked build on the target computer to test and debug a driver during the initial phases of its development.
• Use the free build on the target computer to test and debug your driver during the final phases of its development. The final testing of your driver must be done on a free version of the driver running the free build of Windows NT.

The extra protection of the checked build of Windows NT carries some penalties. Because of the additional error checking code and debugging information, the checked binaries are larger and run slower than the free binaries. This can conceal synchronization or other timing-related problems, such as race conditions, that become apparent only in the free build.

If you run the checked build of Windows NT without having enabled kernel debugging, unexpected system shutdowns can occur. This is because the additional checks in the checked build increase the likelihood of encountering a breakpoint.

The checked build of Windows NT 4.0 Service Pack 6a has been posted to the following Internet location: For additional information on how to obtain the free build of the latest Windows NT 4.0 service pack, click the article number below to view the article in the Microsoft Knowledge Base: