Process bound:
An excessive amount of processing in the CPU that causes an imbalance between I/O and processing. For example, recalculating a spreadsheet, compiling a program or converting a large graphics file can make a desktop computer process bound.
In a multitasking system, process-bound applications slow down other applications and other users depending on how the operating system slices time (see preemptive multitasking).
CPU bound:
In computer science, CPU bound refers to a condition where the time to complete a computation is determined principally by the speed of the central processor and main memory. This means that the computation is keeping the processor utilization high, and that the processor is not spending much time waiting for interrupts, such as those generated by the arrival of more data from a peripheral device. If a program is CPU bound, it has the potential to run faster provided that a better algorithm can be found to accomplish the computation, or if a faster processor/memory can be used.
The usefulness of the distinction between IO bound and compute bound is based on the empirical observation that many of the uses of computers involve doing a small amount of work to each element of a large set of data, which led to the conclusion that such problems are inherently IO bound. Increasing processor utilization has economic benefits, therefore this observation resulted in a search for techniques to increase processor utilization by minimizing the impact of IO delays. This led to the development of multiprogramming and preemptive scheduling.
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 of time spent waiting for input/output operations to be completed. This is the opposite of a task being compute bound. This circumstance arises when the rate at which data is requested is slower than the rate it is consumed or, in other words, more time is spent requesting data than processing it.
I/O Bound As An Inherent Problem in Computing
The I/O bound state has been identified as a problem in computing almost since its inception. The Von Neumann architecture, which is employed by almost all computing devices ever conceived, is based on a logically-separate central processor Unit which requests data from main memory, processes it and writes back the results. Since data must be moved between the CPU and memory along a bus which has a limited data transfer rate, there exists a condition that is known as the Von Neumann bottleneck. Put simply, this means that the data bandwidth between the CPU and memory tends to limit the overall speed of computation. In terms of the actual technology that makes up a computer, the Von Neumann Bottleneck predicts that it is easier to make the CPU perform calculations faster than it is to supply it with data at the necessary rate for this to be possible.
In recent history, the Von Neumann bottleneck has become more apparent. The design philosophy of modern computers is based upon a physically-separate CPU and main memory. It is possible to make the CPU run at a high data transfer rate because data is moved between locations inside them across tiny distances. The physical separation between CPU and main memory, however, requires a data bus to move data across comparatively long distances of centimetres or more. The problem of making this part of the system operate sufficiently fast to keep up the CPU has been a great challenge to designers.
I/O Bound As A Practical Problem
The I/O bound state is considered undesirable because it means that the CPU must stall its operation while waiting for data to be loaded or unloaded from main memory. With faster computation speed being the primary goal of new computer designs and components such as the CPU and memory being expensive, there is a strong imperative to avoid I/O bound states and eliminating them can yield a more economic improvement in performance than upgrading the CPU or memory.