Cycle stealing is an action in which a computer process directly accesses the central processing unit (CPU) to get resources needed to complete the process. This normally occurs when a computer is not being used; the CPU will take advantage of the downtime to run needed processes. When a process needs resources, it generally takes quite a bit of time to get them, but this system considerably shortens the search. While this system has proven useful in some ways, it generally leads to system degradation that causes parts of the computer to become incapable of reaching the CPU. These errors, and the fact that CPUs typically can perform a similar task without these problems, mean cycle stealing is not commonly used.
Desktop computers and sometimes laptops often are kept on during the day, even when people are not directly using them. While many people use their computers often while they are on, there are very few who use a computer 24 hours straight. This results in downtime during which the system is on but not being used, and this is when cycle stealing will occur in computers that have the ability. This is because the stealing process often takes up much of a computer’s resources, and this would lead to very poor speeds if a person were accessing programs at the same time.
When a process needs the CPU, it often goes through a somewhat long chain of events. The process begins by getting a bus protocol, which is held until the last process gets resources. After the CPU goes through a clock cycle, it releases the memory, which goes back through the bus and to the process. In cycle stealing, the process skips most of that and goes directly for the clock cycle from the CPU.
Completing long processes when users are away has many benefits, but cycle stealing system has proved too ineffective for widespread usage. This is because, constant use of the CPU leads to system degradation. Slower processing is one of the smaller problems, while the inability of certain memory channels to connect with the CPU is a larger problem.
Beyond these failures with cycle stealing, there is another reason why this system is not commonly used. Some CPUs are able to divide their power to different buses, so there is little reason for cycle-stealing function with newer computers available in 2011. Computers also are used more during the workday, and businesses usually want the computers off when the day is over to save electricity, so there is not as much time for processes to directly take resources from a CPU.