2 Computer Architecture and Memory Flashcards
2.1.1
What is the CPU?
CPU stands for the Central Processing Unit and acts as the brain of the computer. It processes input, manages data storage, executes instructions.
2.1.1
What is inside the CPU?
- CU
- ALU
- MAR
- MDR
- Cache (typically)
2.1.1
What is the ALU?
ALU stands for the Arithmetic Logic Unit. It carries out arithmetic and logic operations, such as addition, subtraction and comparisons.
2.1.1
What is the CU?
- CU stands for Control Unit.
- It coordinates the operations of the CPU, including fetching, decoding, and executing instructions.
- It controls the flow of data within the CPU.
- It decodes instructions in the machine instruction cycle
2.1.1
What is the MAR?
MAR stands for Memory Address Register.
It holds memory addresses of data that is about to be written to or read from RAM.
It also contains the memory address of the next instruction that the CPU will execute.
2.1.1
What is the MDR?
MDR stands for Memory Data Register. It temporarily holds data that has been read from or is to be written to computer memory.
2.1.2
Describe primary memory
Primary memory provides data storage which holds data and instructions that are currently in use. It usually refers to memory that is directly accessible by the CPU (usually RAM)
2.1.2
Define RAM
RAM stands for Random Access Memory and is volatile. RAM is used to hold data and instructions that are currently in use such as open documents or programs currently in use.
Volatile means that data is only maintained when the device is powered.
2.1.2
Define ROM
- ROM stands for Read Only Memory and is non-volatile.
- ROM stores data and instructions permanently, and the memory store can be read from but not written to.
- ROM contains information that is essential for the computer’s operation, such as instructions for the boot-up process
2.1.3
What is cache memory?
Cache is a small volatile memory store which stores frequently accessed data and instructions. It is located inside the CPU or very close to it so it provides very quick access to data.
- It enhances CPU preformance because it reduces the time spend waiting for data retrieval.
- It also reduces power consumption because accessing data from a cache consumes less power compared to accessing data from main memory or external storage devices.
2.1.4
Explain the fetch stage of the machine instruction cycle
The CPU fetches the instruction from memory. The Program Counter (PC) holds the memory address of the next instruction to be executed, and this address is transferred to the MAR. Then, the MAR communicates with main memory to fetch the instruction. After the instruction is fetched, it is stored in the MDR.
2.1.4
Explain the decode stage of the machine instruction cycle
The instruction is decoded and interpreted in the CU, which decides how to execute the data.
2.1.4
Explain the execute stage of the machine instruction cycle
The CPU performs the actual operation specified by the instruction. This may involve:
* arithmetic or logic operations which is carried out by the ALU.
* memory operations (read or write). The memory location of the data that will be read from / written to is placed in the MAR. And the data is transferred to or from the MDR, depending on whether the instruction is a read or write.
* other computational tasks.
2.1.5
Identify the need for persistent storage (secondary memory)
Secondary storage is needed to provide non-volatile, high-capacity storage for data, programs, and files that must be preserved even when a computer is powered off. Examples of secondary storage include hard disk drives and USB sticks.
2.1.5
Explain virtual memory
Virtual memory is the use of secondary storage as additional primary memory. There are times when the amount of RAM needed to hold all running programs and data is greater than the amount of RAM available to the computer. When this happens, part of the computer’s secondary storage, such as the hard disk, can be used to store data temporarily.
