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Currently I'm a it confused. A IC (integrated Circuit) Chip implements one or many circuits on a chip in order to control any kind of stuff. However, a CPU is from my point of view also a BIG circuit collection. Both are fed with signals in order to control or calculate any kind of stuff.

So when do I call it CPU and when IC-Chip.

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    \$\begingroup\$ Both of your definitions are incorrect. \$\endgroup\$ – Ignacio Vazquez-Abrams Sep 17 '15 at 2:22
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    \$\begingroup\$ A generally accepted difference would be that a CPU focuses on computing data and relies more heavily on external peripherals to store data (eg hdisk) etc. While a microcontroller is more self-contained ( eg eeprom to store data) etc. Both can take a rannge of input but are still ICs. At the other end of the spectrum are more specialised IC like 555 timers and voltage regulators. Much more limited in input and output but still contain multiple transistors etc and therefore are still ICs but you would not call them CPU or MCU. \$\endgroup\$ – BenG Sep 17 '15 at 3:01
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All CPUs are ICs. Not all ICs are CPUs.

This is similar to "All cars are motor vehicles; not all motor vehicles are cars".

A CPU is an IC (or multiple ICs - see update below), which is able to do calculations based on instructions in memory, and can thus be reprogrammed. Most other ICs do one particular thing - serial in, parallel out, accellerometer, 555 timer, etc.

UPDATE - as was correctly pointed out, some CPUs are made up of multiple ICs. I had never heard of this, and I do not know if this still happens - it seems to me as a limitation of technology of days past.

I guess, in summary, a CPU is a function (i.e. is defined by what it does - follow instructions in memory) whereas IC is a technology (i.e. what it is - a circuit on a chip).

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    \$\begingroup\$ 'CPU' does not necessarily refer to an IC. \$\endgroup\$ – alex.forencich Sep 17 '15 at 2:36
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    \$\begingroup\$ Actually, back in the Dark Ages (ca 1975 - 1985) some CPUs were built from multiple ICs. \$\endgroup\$ – WhatRoughBeast Sep 17 '15 at 2:37
  • \$\begingroup\$ en.wikipedia.org/wiki/POWER1 6502.org/users/dieter/mt15/mt15.htm \$\endgroup\$ – Ignacio Vazquez-Abrams Sep 17 '15 at 2:38
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    \$\begingroup\$ You are right - "CPU" can also refer to the communist party of Ukraine. From the context of the question, and the name of this group, I decided that he was asking about the chip, not the box. Using "CPU" to refer to the "box" part of a computer (as opposed to the various peripherals) is called "synecdoche" - "A figure of speech in which a term for a part of something refers to the whole of something, or vice versa.". \$\endgroup\$ – AMADANON Inc. Sep 17 '15 at 2:40
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    \$\begingroup\$ He's not referring to the box. There are many examples of CPUs implemented on multiple ICs. With each IC being a necessary but incomplete part of what is typically defined as a CPU \$\endgroup\$ – crasic Sep 17 '15 at 5:33
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CPU means 'central processing unit', so any component which is 'central' to a system and does most of its processing can be called a CPU. For example, a microprocessor can be called a CPU. However, that same processor when installed in a supercomputer with 10,000 sockets, isn't really considered a CPU anymore, merely a compute node. However, CPU does not have to refer to a chip - it could also refer to a whole board or chassis, especially with old computers before ICs existed or were dense enough to contain a complete processor. It can also refer to the part of a chip that actually does the processing, as in a microcontroller or system-on-chip that has many components integrated on the same die, in addition to a processor. So it occasionally refers to chips, but it does not have to.

An IC, on the other hand, could possibly refer to a CPU, but there are many ICs that are not CPUs. A CPU specifically executes instructions of a computer program, and there are many chips that do not do this. For example, your computer also has RAM, which stores data and does not carry out any processing. There are also a great number of analog and mixed-signal integrated circuits that only implement specific functions, such as amplifiers, data converters, regulators, power supply controllers, timers, serializers, deserializers, multiplexers, etc.

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