Early computers such as the ENIAChad to be physically rewired to perform different tasks, which caused these machines to be called "fixed-program computers". The "central processing unit" term has been in use since as early as

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The fundamental operation of most CPUs, regardless of the physical form they take, is to execute a sequence of stored instructionsthat

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Hardwired into a CPU's circuitry is a set of basic operations it can perform, called an instruction set. Such operations may involve, for example,

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Cloud computing can involve subdividing CPU operation into virtual central processing units (vCPUs ).
A host is the virtual

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The performance or speed of a processor depends on, among many other factors, the clock rate (generally given in multiples of hertz) and the instructions per clock (IPC), which together are the factors for the instructions per second(IPS) that the CPU can perform. Many

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• Addressing mode
• AMD Accelerated Processing Unit
• CISC
• Computer bus
• Computer engineering

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1. ^ Integrated circuits are now used to implement all CPUs, except for a few machines designed to withstand large electromagnetic pulses, say from a nuclear weapon.

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