computer science
Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to Applied science, practical discipli ...
, a
computer
A computer is a machine that can be programmed to Execution (computing), carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as C ...
is CPU-bound (or compute-bound) when the time for it to complete a task is determined principally by the speed of the
central processor
A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, ...
: processor utilization is high, perhaps at 100% usage for many seconds or minutes.
Interrupt
In digital computers, an interrupt (sometimes referred to as a trap) is a request for the processor to ''interrupt'' currently executing code (when permitted), so that the event can be processed in a timely manner. If the request is accepted, ...
s generated by peripherals may be processed slowly, or indefinitely delayed.
The concept of CPU-bounding was developed during early computers, when data paths between computer components were simpler, and it was possible to visually see one component working while another was idle. Example components were CPU, tape drives, hard disks, card-readers, and printers. Computers that predominantly used peripherals were characterized as
I/O bound
In computer science, I/O bound refers to a condition in which the time it takes to complete a computation is determined principally by the period spent waiting for input/output operations to be completed. This is the opposite of a task being CPU bo ...
. Establishing that a computer is frequently CPU-bound implies that upgrading the CPU or optimizing code will improve the overall computer performance.
With the advent of multiple buses, parallel processing,
multiprogramming
In computing, multitasking is the concurrent execution of multiple tasks (also known as processes) over a certain period of time. New tasks can interrupt already started ones before they finish, instead of waiting for them to end. As a result ...
graphics cards
A graphics card (also called a video card, display card, graphics adapter, VGA card/VGA, video adapter, display adapter, or mistakenly GPU) is an expansion card which generates a feed of output images to a display device, such as a computer moni ...
, advanced
sound cards
A sound card (also known as an audio card) is an internal expansion card that provides input and output of audio signals to and from a computer under the control of computer programs. The term ''sound card'' is also applied to external audio ...
and generally, more decentralized loads, it became less likely to identify one particular component as always being a
bottleneck
Bottleneck literally refers to the narrowed portion (neck) of a bottle near its opening, which limit the rate of outflow, and may describe any object of a similar shape. The literal neck of a bottle was originally used to play what is now known as ...
. It is likely that a computer's bottleneck shifts rapidly between components. Furthermore, in modern computers it is possible to have 100% CPU utilization with minimal impact to another component. Finally, tasks required of modern computers often emphasize quite different components, so that resolving a bottleneck for one task may not affect the performance of another. For these reasons, upgrading a CPU does not always have a dramatic effect. The concept of being CPU-bound is now one of many factors considered in modern computer performance.
See also
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I/O-bound
In computer science, I/O bound refers to a condition in which the time it takes to complete a computation is determined principally by the period spent waiting for input/output operations to be completed. This is the opposite of a task being CPU bo ...