103a-at PC Lab

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Open It Up! Lab
Joanna Johnson
Partnered with Amber Tanudjaja
September 22 nd, 2008


The Main Parts Inside a Computer, and How They Work

Processor

Photos here

Processors (also known as the CPU, and when on a single chip as a microprocessor) deal with data and execute stored program instructions. Microprocessors are silicon chips that contain millions of transistors. The first microprocessor, built in 1971, was called the Intel 4004, and processed four bits at a time. Intel is the company's name; later microprocessors introduced by the same company have been called Pentium processors. The processor's actions are synchronized with the crystal's clock ticking; each tick corresponds to a single action from the processor. Modern processors run at about 4 GHz (Hertz is a measure of frequency, specifically the number of times an operation occurs in a second. Megahertz corresponds to millions of hertz; gigahertz to billions of hertz).

Memory

Photos here

Memory technically means any method of electronic storage used with the computer, but it more commonly means quick, temporary storage for the programs and data actively being used. There is a hierarchy of memory storage methods in the computer. First is the hard drive, which provides the most memory at the cheapest cost, but is slow. Next is RAM, or random-access memory. (This term comes from when there were two types of memory, random and sequential, meaning that the data could only be accessed in a certain order.) Like the hard drive, RAM is relatively slow in that it can't run as fast as the CPU. Yet is has the advantage of directly accessing data; there isn't any physical parts that have to move first, such as a disk to spin. Information is stored at locations, each of which have an address so that they can be found. In modern computers, each location holds two bytes of data. The memory chips are circuits made of millions of transistors and capacitors, which hold electrical energy as a bit of data. The transistor acts as a switch, allowing the chip's control circuitry to read the capacitor or change it.

Hard Drive

Photos here

The hard drive stores roughly 120 to 1,000 GB of information. It consists of the platter, a round disk that spins like a record, and a read-write head, which hovers over the surface of the platter to read or write data on it. The platter's surface is magnetically charged; the data is stored as positive and negative spots on this in circles. When reading or writing data on the disk, the head hovers over the spot where the data is stored and determines it's charge. The positive and negative correspond to 0 and 1, so each spot is a bit of binary data. Virtual memory is stored on the hard drive; because there is limited RAM memory, data not being currently used is swapped out and added to the hard drive to make space.

CD/DVD Drive

Diagram of the optical drive, found at http://www.tweak3d.net/articles/opticals/

Photos here

CD/DVD drives (also called optical drives) use lasers to read and write data from aluminum-coated disks. To read the data on a disk, the optical pickup shines a laser on it. How the light reflects determines the data; the light scatters when it hits pits, and reflects back when it hits smooth areas called lands. Each pit or land is a bit of information, for whether the light comes back or not can be written as 1 or 0, binary information. To burn data onto a disk, the laser heats selective areas of it. This changes the reflexivity of the dye on the disk, creating the areas where light either scatters or returns. A CD-ROM can hold about 670 MB of recorded information.






Power Supply

Photos here

The power supply box converts alternating current (AC) electricity from an external source to direct current (DC), the form of electricity computers use. The AC voltage is usually around 100-120 V (it's higher in Europe), and is converted to different voltages for use by different parts of the computer: 3.3 V and 5 V for the digital circuits, and to 12 V to run motors, disk drives, and fans. Many power connecters carry the electricity from the power supply box to other parts of the computer. Two connecters, called PC Main and ATX12V power the motherboard. The Berg connecter powers the floppy drive. Peripheral connecters supply the disk drives with power. There are also several auxiliary connecters to provide additional power if necessary. Also in the power supply box are heat sinks and fans, which help disperse the heat generated when the power box is running.

Cables

Photos here

The cables inside our computer were ribbon cables, flat clusters of parallel conducting wires. They were used to connect the peripherals, such as the hard drive and CD drive. Because their flat shape makes them hard to handle, they're not used to connect to external devices outside of the computer.

Motherboard

Photos here

The motherboard is like the grand connecter of the computer: it allows the different parts of the computers to communicate with each other and receive power. There are many different parts to the motherboard. The chipset, called the northbridge and the southbridge, connect the CPU to the motherboard (and therefore the rest of the computer). The BIOS (Basic Input-Output System) controls the computer's basic functions; when the computer is first turned on, the software that runs first is in the BIOS. The real-tim clock chip supports the basic settings and system time. A bus is a circuit that connects different parts of the motherboard. Bus speed is counted as the amount of data that can move through the bus at once; it's most often measured using the front-side bus, which connects the CPU to the northbridge. The FSB runs anywhere between 66 and 800 MHz (Megahertz).

Battery

Battery from stock photos

The Battery is located on the motherboard, and powers the real-time clock (RTC). The RTC keeps track of the actual time (as opposed to the system-regulating clock of the crystal). This is what allows a computer to display the correct date and time after it has been shut down and the power turned off. The battery also powers the CMOS, an electronic circuit that saves a limited amount of system information after the power is shut down.






Crystal

Crystal from stock photos

The crystal is located on the motherboard, and synchronizes operations. It ticks at a regular number of clock ticks per second; with each tick there is a corresponding action from the CPU. Therefore, a higher clock frequency means that the CPU will work faster, and data will move more quickly. Recently-made crystals have a clock frequency somewhere around 3 GHz; single clock cycle lasts only for a few nanoseconds. The crystal is made of a resonant circuit and an amplifier.





References

  • Processor

"How The Computer Works: The CPU and Memory" http://homepage.cs.uri.edu/faculty/wolfe/book/Readings/Reading04.htm

"Computer Concepts and Terminology" http://www.unm.edu/~tbeach/terms/processors.html

"The CPU: developments and improvements" http://www.karbosguide.com/hardware/module3b1.htm

"Pentium" Wikipedia http://en.wikipedia.org/wiki/Pentium

Brain, Marshall "How Microprocessors Work" How Stuff Works http://en.wikipedia.org/wiki/Pentium

  • Memory

"Computer Concepts and Terminology" http://www.unm.edu/~tbeach/terms/memory.html

Tyson, Jeff and Coustan, Dave "How RAM Works" How Stuff Works http://computer.howstuffworks.com/ram1.htm

"Random-access memory" Wikipedia http://en.wikipedia.org/wiki/Random_access_memory

Tyson, Jeff "How Computer Memory Works" How Stuff Works http://computer.howstuffworks.com/computer-memory.htm

  • CD/DVD ROM

Nguyen, Tuan "How Optical Drives Work" Tweak3D http://www.tweak3d.net/articles/opticals/

"Optical Disk Drive" Wikipedia http://en.wikipedia.org/wiki/Optical_disc_drive

  • Hard Drive

Brain, Marshall "How Hard Disks Work" How Stuff Works http://computer.howstuffworks.com/hard-disk.htm

  • Power Supply

"Power Supply Unit (Computer)" Wikipedia http://en.wikipedia.org/wiki/Computer_power_supply

Brown, Gary "How PC Power Supplies Work" How Stuff Works http://computer.howstuffworks.com/power-supply.htm

  • Cables

"Ribbon Cables" Wikipedia http://en.wikipedia.org/wiki/Ribbon_cable

  • Motherboard

Wilson, Tracy, and Johnson, Ryan "How Motherboards Work" How Stuff Works http://www.unm.edu/~tbeach/terms/memory.html

  • Battery

"Why Does My Computer Need a Battery?" How Stuff Works http://computer.howstuffworks.com/question319.htm

  • Crystal

"Clock Generator" Wikipedia http://en.wikipedia.org/wiki/Clock_generator

Taking Apart the Computer

1.To start, we opened the computer case. This was harder than it sounds; it didn't immediately crack open, and it took a lot of prying to force it off. Once it was open, I was surprised at how much empty space was inside of the tower.


2.Next we started to unscrew the metal units holding the different sections of the computer. We took out the external hardware/bus unit, and flipped up the power supply so we could get at the parts underneath. We also took out the plastic latches. We worked on different sides of the computer, Amber on the front and I on the back.

Metal frame holding the bus and external hardrive

103a-at pic2.jpg


3. We took out the hard drive.

The hard drive


4.Next we took out the cd, floppy, and zip drives, which were all connected to the front of the computer. It was interesting to see the different devices for reading data all next to each other.

The floppy drive
The half-emptied computer case

5.Then we unscrewed the fan, the power supply box, and eased out the mother board. It was surprising how hard it was to find the screws -- they would be tucked underneath other parts that had to be unscrewed first, such as the CPU and motherboard. Some of the screws didn't actually come out even after they were unscrewed, which was confusing.

The Fan
View from the back of the computer case at the hole where the power supply box had been

6. Lastly, we unscrewed the motherboard and took apart what we could of the power supply box, which held a second fan. We couldn't force the CPU apart from the heat sink it is connected to.

The mostly-empty box

The opened power supply box


Memory

SIMM memory

103a-at pic35.jpg


Power Supply

The closed power supply box
The box opened up


Hard Drive

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103a-at pic30.jpg


CD/DVD Drive

The CD/DVD Drive


The CD/DVD Drive, from the back



Zip Drive

The Zip Drive
The Zip Drive


Mother board

The Motherboard, with the CPU still attached
The Motherboard, CPU-free


Central Processing Unit

The CPU attached to the motherboard
Side View of detached CPU, heat sink is underneath

Computer Cables

103a-at pic26.jpg
103a-at pic27.jpg


Other Interesting Photos

Another view of the bus and external hard drive
The motherboard still in the computer case
The external hard drive
The back of the external hard drive