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Basic Hardware Overview

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System Case

• The major hardware components of the computer, as opposed to the I/O devices and other peripherals, are housed in the case. – Also known as chassis or enclosure or system unit.

• The case helps keep the components clean and cool.

• It can also provide some shielding to undesired outside voltages.

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Case with side panel removed.

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More than just a box

• At first the case strikes one simply as a container, but it has some structure.

• If one is building a PC, the case has to be coordinated with the motherboard one chooses.

• The case will also determine how much access there is to the front and back of the PC – the number of bays, expansion slots and so on.

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• Cases come is various sizes and shapes, known as “form factors”– Micro tower, mini tower, mid tower, full tower,

microATX desktop, and ATX desktop.

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Power Supply

• Computers work by having a value – in binary computers a high or low – represented by some physical quantity.

• The physical quantity is typically an electronic voltage or electronic current.

• Thus we need some part of the computer responsible for supplying electronic voltages and/or currents. This is the power supply.

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Power Supply is really a transformer• As far as the other parts of the computer are concerned the

power does come from the power supply – except for a few parts that have a separate battery.

• However, strictly speaking the device known as a power supply does not supply power, it transforms it. The source of the power is a generating station, the power is then delivered to buildings and made available at wall outlets. The power supplied by the outlet must be transformed into the form that is useful for computers. – One could also complicate the scenario with an

Uninterruptible Power Supply (UPS) or a back-up generator.

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AC-DC

• The outlet supplies somewhat high-voltage AC (alternating current) – In the US, the AC supplied is known as 110, it varies

from approximately a positive 156 volts to a negative 156 volts many times a second.

– 156 is the peak voltage, 110 is the rms (root mean square) voltage

• Computers need low-voltage DC (direct current) – Various components need differing amounts of steady

voltage (12 volts, 5 volts, ±3.3 volts, etc.)

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Caution• Because of the relatively high voltages

coming in and the way in which transformation is done, power supplies can be dangerous.

• Do not open up a power supply, unless you have been trained.

• Usually if a power supply goes, it is replaced as a unit.

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Power to the components

• The transformed power must in turn reach the components that use it: – The motherboard and the devices thereon– The various drives (floppy, hard disk, CD) – Etc.

• There is a special (larger) connector to the mother board.

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Molex and Mini Connectors

• The drives are connected with the smaller Molex connectors and the even smaller Mini connectors.

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Parts of a Power Supply

Molex Connector

Mini Connector

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Motherboard• A circuit is a path or paths which current takes through a

set of electronic components (resistors, capacitors, transistors, etc.).

• If a number of the components are etched into a semiconductor, this is called a chip or integrated circuit.

• If a circuit or circuits are printed onto a board, this is called a circuit board. – Sometimes one inserts chips into boards.

• The main circuit board is a computer is known as the motherboard.

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The place to meet• The major components are on the motherboard or

plug into it. • The motherboard has places for processor,

external cache and memory to plug into. • These components interface with other

components via the chipset. • The chipset leads to the controllers of various

other components (hard drive, CD, etc) and to expansion slots so that other circuitry can be added making the PC customizable.

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Chipset• Most of the manipulation of data is done by the

processor. The rest is mostly moving data around. And the main traffic cop is the chipset.

• The chipset allows the storage and input devices to interface with the processor, memory and cache.

• The chipset will determine which processors can be used in the PC, how much cache and memory are allowed, etc.

• Since the chipset interfaces the components with vastly different speeds, it can be crucial is determining a PC’s performance.

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Controllers• Whereas the chipset is a centralized, generic data-

flow manager; controllers are individual, specific data-flow managers that allow one to interface with specific devices.

• Hence one has a floppy controller, a keyboard controller, and so on. – This has changed to a more generic USB controller

with various USB devices

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USB Controller

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Buses• If the motherboard’s chipset and controllers are the

traffic cops, then the motherboard’s buses are the streets.

• Since so many devices want to interface with the processor, there is a set of shared channels for information going to or coming from the processor. These are the buses.

• Like streets, they can vary in speed and capacity. There are fast buses for fast devices and slow buses for slow devices.

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BIOS

• The Basis Input/Output System or BIOS is firmware (instructions burned into ROM) that interfaces between the various hardware components on and plugged into the motherboard and the operating system.

• This layering means that the operating system is not dependent the specifics of the hardware.

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BIOS

• The BIOS is written in ROM because it rarely changes. It may be in EEPROM (Electrically Erasable Programmable Read-Only Memory) so that it can be changed occasionally – flashing the BIOS.

• Being ROM also implies that these instructions are non-volatile – not lost when the power goes off. Thus the instructions for starting the PC are written in this way.

BIOS to be replaced by UEFI

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Processor

• The processor, a.k.a. the Central Processing Unit or CPU interprets the instructions it finds in memory (programs) and responds to and modifies (i.e. processes) the information and directs the other components how to respond.

• The CPU is sometimes thought of as consisting of two parts: – The Arithmetic Logic Unit (ALU)

– Control

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Pentium 4

Intel® Core™ i7 Processor Extreme Edition

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Processor• The processor is the most important chip in a PC

– often called the brain of the computer. • The processor has a lot of contacts called pins

which plug into the motherboard and allow electronic information to flow to and from the processor.

• The pins are arranged in rows around the chip’s perimeter in what is known as the Pin Grid Array PGA. – There have been variations on the “pin” idea, since the

traditional notion of a pin (a long. thin piece of metal) is easily bent.

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Processor features

• Two of the main features of processors are their speed and their instruction set.

• Instructions are broken down into their smallest steps and the processor speed determines the amount of time required for one of these smallest steps.

• A processor’s instruction set is the collection of basic things it knows how to do.

• More recently another main feature of processors has become the number of cores.

Processor features

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System Memory• The processor executes instructions. The

combination of instructions can be varied – that is, computers can be programmed.

• The combination of instructions as well as the data that the processor is currently acting on are held in memory.

• Memory can be distinguished from storage by its intimate connection to the processor and by its volatility – data in memory, Random-Access Memory (RAM) is lost when the power goes off.

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Cache• There are two basic types of RAM

– Static RAM (SRAM) is fast but expensive– Dynamic RAM (DRAM) is slow but cheap

• The processor’s speed is faster than main memory which is made of DRAM. A special unit of faster SRAM memory that works even more intimately with the processor than memory is known as cache.

• Cache is a very sophisticated game of guessing what instructions and data the processor will next need and placing it in the location that can be accessed more efficiently.

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Storage• Memory is essential (otherwise computers would not

be programmable), storage is simply a convenience and was not a part of the earliest computers.

• But without storage the programs and accompanying data would have to be entered anew each time.

• Storage is nonvolatile (keeps the information) without needing power – so that programs and data can be kept from execution to execution, day to day, year to year.

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Hard disk drive

• The main storage device is the hard disk. • The hard disk uses a magnetic material.

The magnetic property can be placed in two states corresponding to 1’s and 0’s.

• The magnetic state can be determined (read) or set/reset (written) by electronic means, but the state can be maintained without constant electric power.

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References

• http://www.pcguide.com/

• http://www.webopedia.com

• http://www.whatis.com

• PC Hardware in a Nutshell, Thompson and Thompson

• A+ Certification: Exam Guide, Meyers and Jernigan