CSC231 Demolition Lab

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Ashley Smith
CSC 231
Thursday, September 16, 2010

Overview

In this lab, we deconstructed an old Dell desktop computer in order to familiarize ourselves with the various components within the desktop. By doing this hands-on, we were also able to see connections between the different components and their placements within the case in order to gain a better understanding of each component’s purpose (e.g., we could see that the heat sink was placed above the CPU, not just to cool the inside of the computer, but to cool the CPU specifically). By understanding the inner workings of a desktop computer, we are better able to understand Assembly language and its relation to the hardware of the computer.

Parts of the Computer

Central Processing Unit (CPU)

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The CPU executes and carries out computer program instructions and computer functions (e.g., reading data from memory). When executing a program, a CPU follows the following four steps: fetch, which retrieves an instruction from program memory; decode, which decides, from the fetched instructions, what the CPU should do; execute, which performs the steps decoded in the previous process; and writeback, which writes the steps the computer executed to some form of memory for easy access in subsequent program executions. [1] [2]

Today, CPUs are most commonly manufactured by AMD and Intel. The operating frequency (also called clock rate) of the CPU varies, with the first commercial CPU, the Intel 8080, operating at 2MHz (2 million cycles/second), and more recent CPUs operating at around 2.8-4GHz (such as the 2002 Intel Pentium 4) [3].

The power dissipation of a CPU varies based on its clock rate, with faster CPUs necessarily consuming more power (and outputting more heat). An Intel Pentium 4 CPU operating at 2.8 GHz has about 68.4 W of typical thermal power (measured under a "normal" load). [4]. The CPU can thus easily exceed 100 degrees Fahrenheit (the maximum operating temperature of the Intel Pentium 4 is 104 degrees Fahrenheit), hence the need for a heat sink to protect the CPU from the excessively high temperatures it produces. [5].

Random-Access Memory (RAM)

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RAM stores computer data and allows the data to be accessed at random, regardless of physical location (i.e., any data can be accessed at the same speed, regardless of its location). [6] The amount of RAM available depends on the computer, with older desktops from the 90's possessing about 256 MB of RAM to newer desktops possessing between 2 to 8 GB of RAM. The model we took apart had 2 RAM cards, each with 1 GB of RAM.

Hard Disk Drive (HDD)

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The HDD is a storage device for computer data, in which data is encoded magnetically by read/write heads. The hard drive is where all user data is stored (such as documents, pictures, etc.). [7] Much like RAM, the size of the HDD varies based on the computer model, with sizes ranging from 20 MB (found in the early days of the personal computer) to 3 TB (the largest HDD size that currently exists). Today, PC HDD sizes typically range from 500 GB - 1000 GB. ([8]

Motherboard

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The motherboard is the "core" of the computer, holding most of the crucial components and providing connections for peripherals. The motherboard also supplies the electrical connections by which other system components communicate. A laundry list of components included in the motherboard is as follows: sockets for microprocessors, slots for the system's main memory, a chipset used to interface between the front-side bus, main memory, and peripheral buses, non-volatile memory chips, a clock generator, slots for expansion cards, power connectors, and connectors for a mouse and keyboard. Things that plug into the motherboard, such as memory and sound cards, are referred to as daughterboards. [9]

Power Supply Unit

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(The PSU is pictured in the rightmost corner, from where the various wires are protruding.)

The PSU, very simply, supplies power to the components of the computer. The PSU takes in about 100-127 V (in North America, Japan, Taiwan, and parts of South America) or 220-240 V (in the rest of the world) of AC power and outputs 5 V or 12 V of DC power to the computer's components. Typical power ranges vary between 300 W and 500 W, with niche or high-end units having power ranges from 450 W to 2 kW. [10]

Expansion Cards (Video, Sound, Network)

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(Pictured: video and sound cards; network card not pictured)

The video, sound, and network cards are expansion cards that can be inserted into the motherboard in an expansion slot. [11]. These cards add functionality to the computer in various ways: the video card allow images to be displayed on the output device (e.g., the monitor) [12]; the sound card facilitates input and output of audio signals and also offers external connectors for things such as a microphone [13]; and the network card allows a computer to access a network and provides MAC addresses (a number unique to each network card, used for identification on a network). [14]

Drives (Zip, Floppy, Optical)

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(Pictured: zip drive and floppy drive; optical drive not pictured)

Along with the HDD, the zip, floppy, and optical drives are all storage mechanisms [15]. The floppy drive offers between 70 KB and 200 MB of data storage, which is read and written magnetically onto and from a 3.5 inch, 5.25 inch, or 8 inch "floppy disk" [16]. The zip drive was produced as an alternative to the floppy drive, storing between 250 and 750 MB of data by reading and writing data in a manner that was similar to the HDD read/write processes. The zip drive offers more data storage and faster performance than the floppy drive, but was never popular enough to surpass the floppy drive and was not useful enough to live past the introduction of USB flash drives [17]. Lastly, the optical drive uses laser light or electromagnetic waves to read and write data from and to discs, which usually vary in storage size from a few hundred MB to 1 GB [18]. Among these three drives, only the optical drive remains in common use today.

Miscellaneous

Heat Sinks and Fans

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(Pictured: a heat sink, and a fan, located beneath a green cover in the right of the picture)

Heat sinks are used within the computer to transfer heat from high temperature areas to lower temperature areas through the use of air (produced by a fan). Heat sinks are always used for CPUs, which produce incredibly high temperatures, and are now commonly being used with newer, more powerful graphics processors that are beginning to generate temperatures similar to the CPU. The fan blows air across components and heat sinks in order to disperse hot air throughout (or out of) the computer, so as to keep the temperature inside the case at a safe operating temperature. [19]

Cables

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Various cables can be seen throughout the picture on the right, including the bunches of multicolored cables and the gray ribbon cables. The ribbon cables are used for connecting the HDD, optical drive, and floppy drives to the motherboard. The multicolored cables connect external devices to the PSU. [20]