Computer organisation Flashcards
Purpose of the control unit
Coordinates all activities of the CPU
What does the control unit make extensive use of
Status register and clock
What is the purpose of the status register
Contains information about the state of the processor
What is the purpose of the clock
Synchronises related components by generating pulses at a constant rate
What is clock speed measured in
Hertz (Hz)
What is the purpose of the ALU
Performs arithmetic and logical operations
What are the general purpose registers
Tiny areas of extremely fast memory located in the processor normally designed for a specific purpose
What is the purpose of the program counter
Holds the address of the next instruction to be executed
What is the purpose of the memory address register
Holds the address of the memory location from which data or an instruction is fetched from
What is the memory buffer register
Used to temporarily store the data which is read from or written to memory
What is the purpose of the CIR
Holds the current instruction being executed
How does Von Neumann architecture work
Instructions and data share the same memory space and format, uses a single control unit or processor, one instruction at a time, registers are used as fast access to instructions or data
How does Harvard architecture work
Instruction and data are stored in separate memory units, each has its own bus, reading and writing data can be done at the same time as fetching an instruction, used by RISC processors
What does the accumulator do
stores the result of the ALU
What are buses
Communication channels
What does the address bus carry
Address of instruction
What does the data bus carry
Carries data from and to the RAM
What does the control bus do
Sends control signals from and to the processor
What is the instruction made up of
Opcode + operand
What is the opcode
What we need to do (OPeration)
What is the operand
What do we need to do it to (can contain actual data or an address where the data is found)
In an 8-bit instruction which bit is the addressing mode
4th bit
What bits are the basic machine operation in an 8-bit instruction
1st, 2nd, 3rd bits
In an 8-bit instruction which bits are the operand
5th, 6th, 7th, 8th bit
In an 8-bit instruction how many different Opcode are available
16
What does “fetch” mean in the FDE cycle
The binary code in the program counter is copied to the MAR which is then put through the ram to get a binary code out which then the control bus sends a signal to read the memory, then the binary code gets sent through the data bus into the memory data register and then into the current instruction register
What does “decode” mean in the FDE cycle
The Current instruction register contains the opcode and the operand, then the operand is searched in the decode unit and then searches for the instruction
What does “execute” mean in the FDE cycle
MAR receives the address that is needed by the decode unit and then puts it through the RAM and then through the data bus into the MDR and then into the accumulator after receiving a signal from the control unit
What are the most common types of storage devices
Optical, magnetic and solid state
Which storage device has the most capacity
Magnetic
What are the optical storage devices
Blu-ray, CD and DVD
How do optical storage devices work
They work by being scanned by a laser and data is stored in pits and lands
What are the positives for optical storage
Cheap, light weight, portable
What are the negatives for optical storage
Slow access times, prone to scratches
What are the positives for magnetic storage
Cheap, large capacity
What are the negatives for magnetic storage
Slow access times, fragile
How do solid state drives work
Flow of electricity forcing electrons into floating gates between oxide layers, electrons then change lanes which signifies a 1 or 0
Positives for a solid state drive
Durable, fast access times
What are the negatives for solid state drives
Cost, limited read/writes
Why do magnetic storage devices eventually fail
Moving parts eventually break
