A single-core processor is a microprocessor with a single core on its die. It performs the

fetch-decode-execute cycle The instruction cycle (also known as the fetch–decode–execute cycle, or simply the fetch-execute cycle) is the cycle that the central processing unit (CPU) follows from boot-up until the computer has shut down in order to process instruction ...

once per clock-cycle, as it only runs on one thread. A computer using a single core CPU is generally slower than a multi-core system. Single core processors used to be widespread in desktop computers, but as applications demanded more processing power, the slower speed of single core systems became a detriment to performance. Windows supported single-core processors up until the release of

Windows 11 Windows 11 is the latest major release of Microsoft's Windows NT operating system, released in October 2021. It is a free upgrade to its predecessor, Windows 10 (2015), and is available for any Windows 10 devices that meet the new Windows 11 ...

, where a dual-core processor is required. Single core processors are still in use in some niche circumstances. Some older legacy systems like those running antiquated operating systems (e.g.

Windows 98 Windows 98 is a consumer-oriented operating system developed by Microsoft as part of its Windows 9x family of Microsoft Windows operating systems. The second operating system in the 9x line, it is the successor to Windows 95, and was released to ...

) cannot gain any benefit from multi-core processors. Single core processors are also used in hobbyist computers like the Raspberry Pi and

Single-board microcontroller A single-board microcontroller is a microcontroller built onto a single printed circuit board. This board provides all of the circuitry necessary for a useful control task: a microprocessor, I/O circuits, a clock generator, RAM, stored progr ...

s. The production of single-core desktop processors ended in 2013 with the

Celeron Celeron is Intel's brand name for low-end IA-32 and x86-64 computer microprocessor models targeted at low-cost personal computers. Celeron processors are compatible with IA-32 software. They typically offer less performance per clock speed co ...

G470.

Development

The first single core processor was the Intel 4004 which was commercially released on November 15, 1971 by

Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California. It is the world's largest semiconductor chip manufacturer by revenue, and is one of the developers of the x86 ser ...

. Since then many improvements have been made to single core processors going from the 740kHz of the Intel 4004 to the 2GHz Celeron G470.

Advantages

* Single core processors draw less power than larger, multi-core processors. * Single core processors can be made a lot more cheaply than multi core systems, meaning they can be used in embedded systems.

Disadvantages

* Single core processors are generally outperformed by multi-core processors. * Single core processors are more likely to bottleneck with faster peripheral components, as these components have to wait for the CPU to finish its cycle. * Single core processors lack parallelisation, meaning only one application can run at once. This reduces performance as other processes have to wait for processor time, leading to

process starvation A process is a series or set of activities that interact to produce a result; it may occur once-only or be recurrent or periodic. Things called a process include: Business and management *Business process, activities that produce a specific se ...

Increasing parallel trend

* Single-core one processor on a die. Since about 2012, even most

smartphones A smartphone is a portable computer device that combines mobile telephone and computing functions into one unit. They are distinguished from feature phones by their stronger hardware capabilities and extensive mobile operating systems, whic ...

CPUs marketed are no longer single-core;

Microcontroller A microcontroller (MCU for ''microcontroller unit'', often also MC, UC, or μC) is a small computer on a single VLSI integrated circuit (IC) chip. A microcontroller contains one or more CPUs ( processor cores) along with memory and programmabl ...

s are still single-core, while there are exceptions. *

Multi-core A multi-core processor is a microprocessor on a single integrated circuit with two or more separate processing units, called cores, each of which reads and executes program instructions. The instructions are ordinary CPU instructions (such ...

a 'few' processors on a die, e.g. 2, 4, 8. *

Many-core Manycore processors are special kinds of multi-core processors designed for a high degree of parallel processing, containing numerous simpler, independent processor cores (from a few tens of cores to thousands or more). Manycore processors are u ...

a 'large number' of processors on a die, e.g. 10s, 100s, 1000s. Some specialist

ASIC An application-specific integrated circuit (ASIC ) is an integrated circuit (IC) chip customized for a particular use, rather than intended for general-purpose use, such as a chip designed to run in a digital voice recorder or a high-efficie ...

s/ Accelerators and GPUs fall into this category.

References

Computer architecture Microprocessors Flynn's taxonomy {{computing-stub