A test register is a small section of a central processing unit (CPU) set aside for tasks the processor can initiate when it wants to test itself or run a test on something else. It is one type of a processor register, and not all processors contain such an area. As a general rule, programs do not need to access this area and thus the access level excludes them to prevent exception errors and other issues that may arise if they attempt to use it. Computer users usually do not need to interact with the test register.
Processor registers are areas of storage on a CPU that do not count as part of the computer's memory and are not readily accessible for memory storage. They are available for use by the processor when it needs very fast access to perform a function. In computer specifications, they may not be accessed unless the specifications are extremely detailed. Typically the access level is set high to limit inadvertent access.
Many types of processor register can be seen in place, including debug and control registers. Each area is available for specific CPU tasks and is not used for other functions. The control register, for example, regulates the central processing unit. Unauthorized access could create errors with the CPU and might potentially crash or damage the system. For this reason, the registers are carefully installed and hidden, and the CPU controls them very closely.
If a CPU has a test register, it can use the memory block to run self tests and perform other testing functions. Test registers may be used for a variety of testing that involves the CPU directly. Programs that need to run self tests use memory on other areas of the computer so they do not interfere with the test register. The rapid access is critical in this case, as the CPU may need to run a test and get a response quickly so it does not interfere with the running of the operating system.
Errors in the test register may result in inaccurate results or problems with the CPU. These can compound over time if they are not identified, and eventually the user will need to install a new CPU. Computer technicians have tools available to access the CPU and trace the origins of computer problems, and can determine if components need repair or replacement to get the computer functioning properly. They can also diagnose software and operating system errors and may debug a computer to address user-reported problems.