CSC231 AMT PC Demolition Lab
- 1 PC Demolition Lab Report
- 1.1 Introduction
- 1.2 Main PC Components
- 1.2.1 Motherboard
- 1.2.2 Processor
- 1.2.3 Memory
- 1.2.4 Power Supply Unit
- 1.2.5 Hard Disk
- 1.3 Additional Components
PC Demolition Lab Report
- Angela Tosca
- CSC 231
- Lab date: 9/8/2010
- Lab report date: 9/17/2010
On Wednesday, September 8, 2010, we in CSC 231 opened up a the system unit for a Dell PC. While I did not take down specific information as to which model of PC we were working with, the appearance of the machine as well as the presence of outdated components such as a zip drive gave the impression that it was several years old.
We proceeded to take out and discuss the various different components found inside the computer. Since we will be spending the majority of the semester programming in machine code that directly manipulates the physical storage of data on a computer, as opposed to higher level languages we have worked with in the past, it is especially helpful to have a good understanding of the basic physical architecture of a computer. Toward that a purpose, a catalog of the different parts we encountered follows below.
Main PC Components
The motherboard is a large printed circuit board which spans nearly the entire length and width of the system unit. It is so named because it is the parent for several daughter boards. It is connected to most of the components of the PC, both core and peripheral. Some examples of its features are:
- a pan and heat-sink that house the CPU
- slots into which memory cards, microprocessors and expansion cards may be installed
- power connectors to distribute power from the computer's main supply to the various components connected to the board
- a clock generator which keeps the different parts of the machine synchronized
- connectors to various I/O devices
Description and Basic Functioning
The processor that we looked at is a small integrated circuit manufactured by Intel and housed below a heat sink on the motherboard. It carries out the functions of the CPU, or central processing unit, of the computer.  The CPU, in turn, carries out instructions stored as numbers in the memory of the computer. There are four basic instructions which most CPUs carry out, and they are:
- Fetch: retrieve an instruction from memory
- Decode: translate the instruction into appropriate signals that can be understood by other components of the CPU
- Execute: perform the operation specified by the instruction
- Writeback: write the result back to memory 
The design principle of physically separating program execution from memory storage is referred to as the von Neumann architecture, and is still the dominant form of computer architecture today after first being proposed by mathematician John von Neumann over 60 years ago. By allowing computers to run on stored programs, it makes them more flexible and thus more powerful than their original fixed-program ancestors like the ENIAC. It also, however, introduces a bottleneck, particularly when the computer is performing minimal processing on large amounts of data, in that the throughput between the CPU and memory is very small in relation to the size of the memory. In these cases, the CPU often has to wait as data is transferred back and forth between processor and memory. 
Another thing that makes the microprocessor that we looked at unique in relation to its predecessors is its scale. During the lab, we were shown an older CPU which consisted of a large board with several chips lined on its surface in rows. The microprocessor inside the computer we took apart, on the other hand, is a Very-Large-Scale Integrated device, as opposed to the Large-Scale Integrated device we looked at in class. This means that the microprocessor contains exponentially more transistors upon a smaller surface.  While I could not find an accurate representation of the Large-scale device that we looked at in class, I did find the a picture of a medium scale integration machine, which is pictured above for comparison with the microprocessor.  The CPU is probably one of the groups of circuits in this picture, giving a good idea of scale comparison.
Processing Power and Specs
Unfortunately, I did not take down the actual part number of the processor we examined. The model that we will be discussing in this course is the Intel 8086, which was produced between 1978 and the mid-1990s. It had an operating frequency of between 5 and 10 MHz. 
According to Dell's website, it appears that the processor that would be used in a Dell PC today is the Intel Core Processor. , which operates at a frequency of 2.66 - 3.2 GHz  and dissipates between 73 and 130 Watts .
Description and Basic Functioning
The computer's main memory is stored on modules which contain groups of integrated circuits as pictured to the right (the picture was pulled off Wikipedia's entry on RAM, since we did not have a picture of the RAM for the computer we dismantled in class.) It is referred to as Random Access Memory to indicate that once stored, the data can be accessed at random, regardless of its physical location. This is in contrast with Serial Access Memory devices, such as casette tapes, which store memory sequentially .
DRAM, or dynamic RAM, is one of the most common types of RAM. With DRAM, a capacitor and transistor are paired to store one bit of memory. The term "dynamic" refers to the fact that for the capacitor to hold on to a charge and thus store a bit, it must be periodically refreshed. Memory cells are etched in rows and columns upon a chip, and addressed according to their position.  Again, while DRAM is a very common type of RAM, the term "RAM" is also be used to describe many other types of memory configurations. 
All currently running processes of a computer are stored in RAM.  In more detail, this means that when a process is called, the CPU accesses an executable file from the hard disk (via input/output channels ), executes the instructions , and loads the result to RAM (via a memory bus ) along with any data files handled by the process. 
While I did not collect enough information during the lab to determine exactly how much memory was contained in the computer we took apart, I again referred to the Dell website for information on how much memory is contained in a normal consumer model PC. Dell offers between 4GB and 8GB of RAM on their Inspiron PCs.  By comparison, an iMac comes with up to 16GB of memory (though the smaller MacBook Air only comes with up to 2 GB.) 
Power Supply Unit
The power supply unit converts AC power from a main supply in the wall to DC power that can then be used by the components of the computer. . The outside of the power supply unit of the machine we disassembled in class is visible in the picture displayed to the left. For greater detail, I have also borrowed a picture of the insides of a similar unit from Wikipedia, pictured to the right. 
In both pictures, and air vent is visible, which is necessary because the power supply generates between 300 and 500 watts for a normal computer. In the picture to the right, we can see two heat sinks which convert the heat given off into air  which is then expelled by the vent. Also visible in this picture of the inside of a power supply is the wire bundle which brings power to the various PC components, such as the motherboard and external drives. .
The input voltage for the power supply is 100-127V in North America, and the output voltage depends on the connection. For instance, 12V is used to supply power disk drive motors, and 3.3V is used to supply the motherboard. 
Description and Basic Functioning
The hard disk drive is a magnetic secondary storage device , meaning the information stored within it is not directly accessible by the CPU.  Physically, the hard disk drive consists of two spinning disks, each powered by an electric motor, and a read/write head.
Unlike RAM, the information stored in the hard disk is not lost when the computer is powered down, making it a non-volatile type of memory.  Due to the differences in physical architecture, there is also a significant difference in the time it takes for a computer to access information stored on the hard drive versus information stored in RAM. While information stored in a hard drive is typically accessed within thousandths of a second, information stored in RAM can be accessed within nanoseconds. 
The hard drive that we took out of our machine is a Seagate Barracuda ATA IV with 80GB of memory. Additional specifications are found on Seagate's website  We can also see on another portion of Seagate's site that they now offer hard drives ranging in 300GB to 1TB (1024 GB) in size. 
This is a device that configures the computer for interaction in a local area network. It contains a 48 bit MAC address burned onto a ROM chip  which identifies the computer in the LAN. We can tell from the input jack that this is an ethernet adapter. Based on the label, we can see more specifically that is a FriendlyNet PCI Adapter, model 696, made by the Asante corporation .
The zip drive is a removable storage device that was briefly desirable in the mid-1990s because it offered more storage capacity than a floppy disk at the same size, but which was ultimately replaced by other more portable storage devices in the early 2000s. 
This is an expansion card for processing graphics, as is evident by the connection port for a monitor. Some interesting components of a video card are:
- Graphics Processing Unit which is a powerful processor designed for optimized, fast graphics and which can both render 3D graphics and translate them to 2D graphics.
- Video BIOS which contains the main program for the unit and allows it to interact with the computer and with software
- Video Memory which ranges in modern processors from 128 MB to 4 GB
- RAMDAC, or Random Access Memory Digital-to-Analog Converter, a RAM chip which regulates the functioning of the card
- Outputs, in this case just one
The sound card is specialized for processing audio data and is useful for applications that deal with sound data including games and audio editing software.  We can see that there are several I/O ports here - this is because some of the functions of the sound card include converting digital signal to analog with a DAC converter and then outputting the sound through an amplifier and headphones or speakers, as well as receiving and processing sound data from various inputs such as microphones or casette tape recorders, and then storing the data on the hard drive to be manipulated by various software applications. 
This particular sound card, Creative Labs' Sound Blaster, was instrumental in the development of multimedia technology for the home computer. It was relatively inexpensive, good performing, and compatible with such devices as joysticks and midi controllers. It's popularity made Sound Blaster compatibility and interactive audio capabilities a key feature of many entertainment applications.