Unit 1 Lab 1: Computer Model Understanding Activity
Eric Presnall 11/10/2014

When computer scientist John von Neumann designed his computer model in the 1940s, it was based on two main components: a central processing unit (CPU) and a storage structure (memory).
This is the basis of most computers in use today. The purpose of this architecture was to show how a computer would access and run stored programs that contain programmed instructions and data. These are stored in random access memory (RAM), which can be read from and written to, similar to today’s computer RAM.
Originally, the CPU was broken down into two components: the control unit and the arithmetic unit.
Each component had its own purpose. The control unit reads and interprets a program’s instructions, which are converted into electrical signals that activate other components of the computer. The arithmetic and logic operations.
The memory, which can be randomly accessed by the processor, stores data in cells. The data stored in each cell is a number between 0 and 255. Each one of these numbers is a byte of information. The numbers are actually stored in binary form instead of decimal form.
RAM has many, many cells with which to store these bytes of information.
Data files, programs, graphics, and everything else you work with that is stored on the computer are based on bytes, which are simply any number between 0 and 255.
Different values account for different data. A simple example of this is the capitol letter “A.” In the American Standard Code for Information Interchange (ASCII) character-encoding system, this letter is associated with the number 65. Capitol “B” is associated with the number 66, and so on. Other characters, keys on the keyboard, colors, and everything else are associated with numbers in this fashion. Instruction sets consist of many bytes of information.
So, memory is used to store the numbers. The arithmetic unit calculates those numbers, and the control unit interprets what has been calculated and instructs the rest of the computer to take the necessary actions.
As time went on, the model went through some changes. The biggest change was the interrogation of the control unit and the arithmetic unit into a single component that we still refer to as a CPU.
The terms CPU, processor, and microprocessor are often used interchangeably. Nowadays, processors can be as fast as 2 or 3GHz. If you were able to build a computer, you wouldn’t purchase a separate control unit and arithmetic unit; you would simply purchase a CPU, otherwise known as a processor.
On another note, one inherent problem with the original von Neumann design is the fact that the memory is physically separate from the CPU.
This causes the “von Neumann bottleneck,” a limit on the throughput between the CPU and the memory. The actual bottleneck is the pathways between the two. The CPU is powerful and can calculate lots of data; the memory can store lots of data, but those pathways between the two just can’t handle the amount of data that needs to be sent back and forth. An analog of bottleneck is when you are driving on the highway, inevitably encounter construction, and the highway is constricted from three lanes to one, causing all of the vehicles to slow.
Several ways to alleviate the von Neumann bottleneck were developed. The most common of these was the concept of the memory of cache. Cache memory is located either on, or in, the processor core. It is usually far less in quantity compared to the main memory (RAM), but its proximity to the CPU to store and retrieve the most commonly used data more quickly as compared to storing and retrieving from RAM. Today’s computer’s CPUs might come with 1, 2, or even 8 or 16 MBs of cache memory. Finally, the architecture of the model was expanded to incorporate modem computer’s devices.
Von Neumann originally divided the computer into five main groups.
The following list describes the five groups: * CPU- The “brain” of the computer, responsible for doing the math and telling the rest of the computer what to do. * Working Storage- Generally this is RAM that stores information temporarily. This information is lost when the computer is shut down. * Permanent Storage- ROM, hard disk, and optical disks fall into this category, they store data permanently even when the computer is turned off. * Input Devices- Keyboards, mice, microphones, and other similar devices that are used to input information from the computer. * Output Devices- This included display monitors, printers, speakers, and other devices used to output information from the computer.