103a-be PC Lab

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Emily Everett's PC Disassembly Lab

Welcome to my lab page--Here you will see the exciting process of ripping apart a Dell computer.
You can also view all the different parts that work together to make it work!
My lab partner, Anna, and I had a lot of fun!
103a-be teamwork1.jpg

Open It Up! Lab

The main parts inside a computer, and how they work

  • The Processor
A processor is often referred to as the 'brain' of the computer--and this is not far from the truth. Using transistors, a processor executes instructions in a set order. It uses assembly language, and has the ability to move data to different locations in the
103a-be processor.jpg
memory. The first processor was designed in 1971, and called the Intel 4004. The first processor to be used in a home computer was the Intel 8080, designed in 1974. It had 6,000 transistors, and a speed of only 2 Megahertz. Megahertz are a measure of frequency; hertz are the number of cycles per second, so one Megahertz means that there are 1,000,000 cycles per second. This might seem like a lot, but newer processors are much faster. The Pentium 4 "Prescott," also produced by Intel, was released in 2004--its speed is roughly 3.6GHz, or 3.6 billion cycles per second. The relationship between efficiency and transistors can be seen by comparing the number of transistors on the Pentium 4 processor (125,000,000 transistors) to the number on the Intel 8080 (6,000 transistors). The more transistors a processor has, the quicker it is able to execute instructions and complete functions, and the more cycles per second.

<http://computer.howstuffworks.com/microprocessor.htm> Brain, Marshall. "How Microprocessors Work." 01 April 2000. HowStuffWorks.com. 06 October 2008.

<http://en.wikipedia.org/wiki/Megahertz> From Wikipedia. "Hertz." 04 October 2008.

  • The Memory
103a-be mem.jpg
The memory is used primarily for fast, temporary storage--it contains things that will need to be used at the time, so that they don't need to be retrieved from the hard disk every time they are needed. This is stored in Random Access Memory, or RAM. RAM is measured in megabytes and gigabytes; most typical operating systems only require 128-512 MB of RAM, but servers and other special-use computers require much more. Running the operating system is one of the main jobs of memory; when the computer boots up, the operating system is loaded from the hard disk to memory. Programs and applications are run in primarily the same way--the necessary parts are loaded to memory for easy access, and other parts are brought from the hard disk as they are needed. The 'bit size' refers to how many bytes (a group of 8 bits is a byte) can be accessed at one time. The more bytes, the bigger the bit size, and the faster the memory. Because a byte is 8 bits, a 64 bit CPU processes 8 bytes at a time.

<http://computer.howstuffworks.com/computer-memory.htm> Tyson, Jeff. "How Computer Memory Works." 23 August 2000. HowStuffWorks.com. 06 October 2008.

  • The Disk Drive
A hard disk preserves information in the same way as a cassette tape--magnetically. This is important because digital
103a-be hdisk.jpg
information is not saved once the computer is shut off. Digital information depends on electricity and the on/off capabilities; magnetic information has the advantage of being both very permanent, and easily rewritable. Besides the accompanying electronics, a hard disk contains platters, which contain the magnetic information; a wheel, which spins the platters very fast; and a read-write head. The read-write heads are on an arm that moves back and forth over the platters. This is how the hard disk locates the precise information needed; there are 2 read-write heads for each platter, so it can read both sides. Thus, a typical hard disk with 3 platters has 6 read-write heads. These platters are divided up into tracks, which are concentric circles almost like the grooves on a vinyl record. The platters are also divided into sectors, which are pie-shaped sections of the disk. Each sector contains a set number of bits, and is formatted in different ways by the operating system.

<http://computer.howstuffworks.com/hard-disk.htm> Brain, Marshall. "How Hard Disks Work." 01 April 2000. HowStuffWorks.com. 06 October 2008.

<http://en.wikipedia.org/wiki/Hard_disk> From Wikipedia. "Hard Disk Drives." 06 October 2008.

  • The CD ROM
103a-be cd.jpg
CDROM stands for "Compact disc Read-Only Memory." This is because the memory on a CD is not easily changeable (like the

memory in a computer), and non-volatile, so that it is not lost when powered off. The data on a CD is stored in one long spiral track. On this track are tiny pits, only 100 nanometers deep and 500 nanometers wide. These pits essentially contain binary code; their pit/no pit code works fundamentally like a on/off or 0/1 code. This information is processed using a near-infrared laser. The drive focuses a laser on the track, and reflects off of the pits--obviously in two ways, depending on whether there is or is not a pit where the laser is reading. The optical senses the reflected laser, and in which way it is reflected. The drive than interprets this information in terms of bits--from pits to binary digits.

<http://electronics.howstuffworks.com/cd.htm> Brain, Marshall. "How CDs Work." 01 April 2000. HowStuffWorks.com. 07 October 2008.

<http://en.wikipedia.org/wiki/CD-ROM#CD-ROM_drives> From Wikipedia. "CD ROM Drives." 07 October 2008.

  • The Power Supply
The power supply contains a lot of parts--fans, cables, etc--but its function is relatively simple. It converts the AC (alternating
103a-be psup.jpg
current) from the wall power supply, into DC (direct current), that can be used by the computer for various tasks. With switcher supplies to make their job easier, transformers transfer the energy from the wall, which is about 110 Volts, to a DC form that is greatly reduced. A computer doesn't need 110 Volts--all digital current (binary code, etc) needs only 5 Volts, and mechanical parts (fans, motors in the hard disk and CD drives, etc) need only 12 Volts. Another important function of the power supply is to filter the electricity used in the computer. Because of the sensitive nature of a computer's activities, it is crucial that electricity flows without the spikes and surges that might happen elsewhere. The power supply protects the computer's hardware, and prevents any problems that might result from electrical variations.

<http://computer.howstuffworks.com/power-supply.htm> Brown, Gary. "How PC Power Supplies Work." 05 March 2001. HowStuffWorks.com. 07 October 2008.

  • The Battery and the Crystal
The battery is a very important part of the motherboard. Sometimes it is soldered directly onto the motherboard, but more often now, it is in a separate holder that makes it easier to replace. The amount of time that a battery can last depends on
103a-be rtc.jpg
many different factors, and especially the size. The primary function of the battery is to power the crystal. The motherboard contains the Real Time Clock, which operates a vibrating quartz crystal. Since quartz is a very stable, consistent substance, it is perfectly suited to maintain the correct time for the whole computer. This is important because all the parts of the computer are synchronized from this crystal. The crystals can vibrate at many different frequencies; the most popular are 3.58 MHz and 14.318 MHz, because they combine performance with low cost. Other common frequencies include 10 MHz, 20 MHz, 33.33 MHz, and 40MHz. These measure the frequencies at which the crystals vibrate. A typical small battery in a PC will be able to power the crystal and Real Time Clock for 5-7 years.

<http://en.wikipedia.org/wiki/Crystal_oscillator> From Wikipedia. "Crystal Oscillator." 07 October 2008.

<http://computer.howstuffworks.com/question319.htm> "Why does my computer need a battery?" 01 April 2000. HowStuffWorks.com. 07 October 2008.

<http://computer.howstuffworks.com/pc.htm> Tyson, Jeff. "How PCs Work." 05 June 2001. HowStuffWorks.com. 07 October 2008.

  • The Cables
103a-aj IDE.jpg

Cables are very important in a computer. They serve many diverse purposes, moving power, data, and instructions from one place to another. A power cable brings electricity from the wall to the computer's power supply, and cables take the transformed DC from the power supply to the other parts of the computer that need power. Alternatively, the high-speed serial bus connector transports data from 'input devices' to 'output devices' (in bits, like all data).

Morgan, Elizabeth . "Computer Cables." Ezine @rticles. <http://ezinearticles.com/?Computer-Cables&id=252371>

  • The Motherboard
The motherboard is one of the most important parts of a computer. It contains the Real Time Clock, and the processor. It is
103a-be momboard.jpg
also responsible for running any drives, ports, and peripherals that the computer might have. Essentially, the motherboard is powered from the power supply, and then distributes power to all the circuits and other parts that also require power. It is made mostly of circuits--small wires and gates that use binary code to store information. In addition, the motherboard contains many buses, which are circuits that connect one part of the motherboard to another part. The amount of data that can be moved through a bus at one time is called its speed, and measured in megahertz. For example, the AGP bus connects the computer's video card to memory, and to the processor; its speed is generally 66 MHz.

<http://computer.howstuffworks.com/build-a-computer.htm> Brain, Marshall. "How to Build a Computer." 08 August 2006. HowStuffWorks.com. 08 October 2008.

<http://computer.howstuffworks.com/motherboard.htm> Wilson, Tracy V., and Ryan Johnson. "How Motherboards Work." 20 July 2005. HowStuffWorks.com. 08 October 2008.

Breaking It Down!

On September 22, 2008, we disassembled a black Dell PC.
Following is a general description of what we encountered during this process, and photographs to help the explanation.

  • Opening the outer case--Thankfully, our Dell was relatively easy to take apart, because it has a lot of user-friendly tabs and buttons, as opposed to screws and bolts. By pressing two buttons on the side, we were able to pop open the computer, and take a look inside!
103a-be dis1.jpg 103a-be dis2.jpg

  • At first glance, there seemed to be a lot going on! With all the wires criss-crossing through everything, it was pretty confusing to look at. Our first task, therefore, was to remove all these wires, and simplify what we were looking at. This was relatively easy, because the wires are not too hard to pull off, with a little bit of force. Next we started to remove everything else--the hard disk, CD/DVD Rom, the video interface, memory, and the mother board.
103a-be mother.jpg 103a-be anna.jpg

  • Most of these things were not too hard to remove--The Dell has a lot of green plastic tabs that, when pushed and pulled and pinched, often allow you to remove parts without a screwdriver or a lot of muscle. This was true for the hard disk, the CD/DVD Rom, and the mother board. Other things were not so easy to remove--they required a little pulling and prying, to say the least. The power supply/transformer was quite difficult to remove. Many of the finer parts of disassembly (separating the processor, dissecting the power supply, etc) required more effort that the earlier parts.
103a-be power.jpg 103a-be supply.jpg

  • One of the most surprising things we found is how simple some of the parts are. It is sometimes difficult to believe that such a complex machine runs with such simple mechanisms. The processor really surprised me--the idea that such a tiny, normal looking part is responsible for processing so much information is hard to grasp! I was also interested to learn that the hard disk is so mechanical. The disk is made of two magnetic disks, that spin very fast and are read by an arm. For me, it was surprising that all the information encoded on the hard disk depends on many very mechanical parts--bearings, wheels, etc.
103a-be processor.jpg 103a-be hard disk.jpg

All the Parts!

  • The Mother Board:
    103a-be momboard.jpg
  • The Hard Disk:
    103a-be hdisk.jpg
  • The CD/DVD Rom:
    103a-be cd.jpg
  • The Power Supply:
    103a-be psup.jpg
  • Memory:
    103a-be mem.jpg
  • The Processor:
    103a-be processor.jpg
  • The Processor with cooling component: 103a-be coolproc.jpg


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