P2 T2 L5 Internal Hardware Components Flashcards
What is word length/size? (5 points)
- “Word length/size” refers to the number of bits processed by a computer’s CPU in one go (these days, typically 32 bits or 64 bits).
- Data bus size, instruction size, address size are usually multiples of the word size.
- Memory is divided up in equal units called words
- Word length is usually 8, 16, 32 or 64 bits
- Each word has a separate memory address
Purpose of processor? (2 purposes)
- Executes instructions
- Supervises other components
NOTE:
- Also known as the Central Processing Unit (CPU)
- Multicore microprocessor = the processor will have several cores allowing for multiple programs or threads to be run at once
Purpose of main memory? (1 purpose)
- Main memory is used to store program instruction and data
The CPU will fetch the data and instructions it needs from the Main memory . This known as the _______-_______ _______.
Modern computers will have gigabytes of Main memory, meaning that large programs can run and multiple programs can run at once.
Main memory consists of data stored in ________ _________,
the more main memory you have the more addresses you’ll have and vice versa, meaning the larger the number of programs you can run at once.
fetch-execute cycle
memory addresses
Explain RAM (2 points)
- Random Access Memory can be read from and written to.
- Data is cleared when the power is off (Is volatile).
NOTE:
RAM stores things like User Data, Application Software, System Software (bits of the Operating System, currently in use), System Variables, Buffers, Disk Cache…
Explain ROM (2 points)
- Read Only Memory can only be read from, data is maintained when the power is off (Is not volatile)
- It tends to store core software instructions such as the code needed to load the Operating System into RAM
NOTE:
Whilst RAM might be several gigabytes in size, ROM will often be a few kilobytes.
Explain I/O controllers (3 points)
- An I/O controller is an electronic circuit that connects to a system bus and an I/O device; it provides the correct voltages and currents for the system bus and the I/O device.
- It will translate signals from the device into a format the CPU can understand
- The I/O devices perform slower than the CPU so the I/O controller acts as a buffer, to buffer data between the CPU and the devices, this is to free up the CPU so that it is not waiting for a response.
Examples of I/O devices include:
keyboard controller, attached to a keyboard
disk controller for a Hard Disk (Hard Disks are not main memory!)
video display controller, attaching a video display unit (monitor)
Explain The stored program concept (6 points)
- Data and instructions are both logically the same and can both be stored in memory.
- This enables it to perform a variety of tasks in sequence or intermittently.
- Program instructions are transferred from backing store to main memory.
- Instructions are fetched (in sequence), decoded and then executed.
- A program must be in main memory in order for it to be executed.
- The instructions are fetched, decoded and executed one at a time.
Explain the system bus (3 points)
- A Bus is a series of wires that transfer data signals between internal components.
- This connection will normally consist of multiple wires along which signals, instructions and data will be carried.
- The System Bus consists of 3 separate buses, each with a specific task (that you need to know).
Explain the control bus (5 points)
- Abi-directional bus, typically consisting of more than 16 wires, used to transport control signals between the three components
- Memory read: causes data from the addressed location to be placed on the data bus
- Memory write: causes data on the data bus to be written into the addressed location
- Bus request: indicates that a device is requesting use of the data bus
- Clock: used to synchronise operations
Explain the data bus (4 points)
- The data bus is bi-directional as data can be sent both ways along the bus
- The width of the data bus is defined by the number of wires or lines it contains
- If the data bus is the same width as a computer word, data can be transferred to and from memory in a single operation
- If it is 16 lines and a word is 32 bits, it will require two memory access and data transfer operations
Explain the address bus (4 points)
- This bus carries the address of a memory location in one direction from the processor to I/O controllers and memory
- It may, for example, be the address of the next instruction to be processed, or the address of data referred to in the instruction
- The width of the address bus determines the maximum possible memory addresses of the system
- A 32-bit bus can carry 2^32 (4GiB) addresses
Which ones of these are input devices and which ones are output devices?
A mouse
A monitor
A CD
A printer
A keyboard
Speakers
A light on the base unit
A mouse - Input
A monitor - Output
A CD – Storage so neither!
A printer - Output
A keyboard - Input
Speakers - Output
A light on the base unit - Output
