Components of a Computer : Processor

Computer Components

Central Processing Unit

CPU

The brains

Central Processing Unit: The “brains” of the computer, which performs the primary computations
Some computations may be offloaded to other parts of the computer, but the CPU remains the central area of computation
Each modern CPU consists of hundreds of millions of individual switches, each switch physically constructed as a transistor, with only two states: on or off
Recent CPU’s in mainstream PC’s are multiple-core, which means two or more CPU units on the same chip
Multiple core computers are most efficient when the software is able to support parallel computing, dividing tasks up to run separately on each core

x86 CPU’s

Based on the old classics

PC CPU’s are organized around a very basic instruction set called x86 that dates all the way back to 1978
Became the basis for the very first IBM PC in the early 80’s
Intel dominant for PC (x86) CPU’s Figure: Intel Core i7 Chip.
AMD in 2nd place for PC’s, offers excellent value and full x86 compatibility, and latest Ryzen CPU competes well with Intel
All major PC operating systems – Windows, Mac and Linux – run on the x86 instruction set

Intel PC CPU’s – Mainstream

Mainstream Chip Family: Core i series

Core: Current family of Intel CPU’s from the Core family

◦ i7: The high end, found in the most expensive PC’s

◦ i5: Midrange, plenty of computing power for most

◦ i3: The lower end, but still sufficient for most tasks

Each new generation of Intel CPU’s in the Core family maintains the same i7, i5 and i3 branding, even though there can be significant increases in performance across generations
Always know what generation of CPU you purchase, since the i3, i5, and i7 branding stays the same across generations
Kaby Lake: 7th generation Core CPU, released Fall of 2016, primary advantage is hardware encoded video processing, so much faster at this task
Kaby Lake Refresh: “8th” generation Core CPU, released Fall of 2017

Other Intel PC CPU’s

From the high end to the low end

Xeon: High-end series of Intel chips for workstations/servers
Core X-series announced May 2017, more powerful than mainstream Core CPU’s, includes the brand new i9 chip

Pentium

◦ Older, hotter, less efficient design, but still produced

◦ Probably better to buy a used system at the same price or pay slightly more to move up in CPU power

Celeron, which Intel calls “Affordable entry level computing”

◦ CPU offered in only the cheapest systems

◦ Probably better to buy a used system at the same price or pay slightly more to move up in CPU power

CPU Characteristics

CPU Clock
CPU runs in cycles

The CPU does not compute continuously, but rather in a series of discrete cycles
CPU clock: The master coordinator of the CPU cycles, a conductor that synchronizes the CPU and its communication with other components
Each computer contains a clock in the form of a quartz crystal that vibrates at a specified frequency, each pulse or cycle is a beat, like a metronome

CPU Clock Speed
Number of cycles per second

Each computer instruction requires a fixed number of cycles
Clock speed: Number of cycles per second the CPU executes
The clock speed is measured in cycles per second, or hertz, such as 2GHz, which is 2 billion cycles per second
Overall amount of work accomplished by the CPU depends on both the clock speed and the amount of computing accomplished on each cycle, which varies from CPU type to CPU type
More recent CPU’s run at a slower speed that CPU’s of even the 2006 era, but process more information per cycle

CPU Cache

Cache: High-speed memory area as part of or directly connected to the CPU that keeps a copy of the most recently used data in main memory
On modern CPU’s, 1MB or more, up to 6 or 8MB or so
Purpose is to reduce the average time to access memory
L1 cache is the fastest, is part of the CPU itself and is the first memory accessed by the CPU
L2 cache is directly connected to the CPU, accessed after L1 cache, bigger and slower
L3 is the next level, accessed after checking L1 and L2, bigger and slower

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