Characteristics of contemporary processors Flashcards
A processor contains a number of special registers.
Name and describe three buses used to convey information between the special registers.
Control bus…
…transmits control signals from the control unit (to other parts of the processor)
Data bus…
…carries the data (from one place to another)
Address bus…
…carries the location address (register) where the data is going (to or from)
Explain the need for the following register
PC
–Is needed to store the address of the next instruction (to be processed)
–Value is then sent to the MAR
–After sending the value the PC is incremented / changed to address held in CIR if the operation is a Jump
Explain the need for the following register
MAR
– Contains the address of the instruction (to be accessed in memory)…
– …address of instruction sent from PC
– Contains the address of the data (to be accessed in memory)…
– …address of data sent from CIR
Explain the need for the following register
MDR
– Contains the instruction which has been accessed from memory
– Contains the data which has been accessed from memory
– That is referenced by the MAR / Instruction sent to CIR
– acts as a buffer
Computer architectures use registers including the accumulator. Describe two ways in which the accumulator is used.
Temporary storage
for data being processed / during calculations
I/O in processor…
… used as a buffer / gateway
A processor uses a number of different registers. One of these is the Current Instruction Register.
Describe the use of special registers and their functions during the fetch-decode-execute cycle, including jump instructions, reading from and writing to memory.
Registers:
Mentions CIR MDR MAR PC and ACC
Jump instruction CIR sends address to PC
PC incremented
MDR copies data to CIR
CIR holds the data to be decoded.. …into opcode and operand
Saving:
CIR sends address to MAR.. …sends data to MDR
All data to be saved uses the ACC
Other relevant points:
All arithmetic and logical operations use the ACC
Mention of buses (Address Data or Control)
Control unit for synchronisation Mention of Interrupt Register
ALU performs calculations
A company is designing a new low-power processor to be used in a smartwatch. The processor contains a control unit.
Describe the role of the control unit in the processor.
□ Decodes instructions. [1]
□ Sends control signals to coordinate movement of data through the processor / execute instruction. [1]
□Controls buses [1]
The processor fetches data from memory location 50. Explain how the following are used in the process:
MAR
Address bus
Data bus
MDR
□ Stores the memory location of the data to be fetched/ stores the memory location 50 [1]
□ Transfers the memory location to access the data (to be fetched)/ transfers the memory location 50 [1]
□ Transfers the data from the memory location specified by MAR / Transfers the data from the memory location 50 [1]
□ Stores the data from memory location specified by MAR / Stores the data from memory location 50 [1]
Describe how each of these improves a processor’s performance:
fast clock speed
Gives more cycles per second
More instructions can be executed per second
So the program takes less time to run (1 per -, Max 2)
Describe how each of these improves a processor’s performance:
large cache memory
More space for data / instructions in cache memory
RAM needs to be accessed less frequently
Accessing cache is quicker than accessing the RAM (1 per -, Max 2)
Give a Little Man Computer instruction that will copy the contents of the accumulator into memory when executed
STA
A student, Dan, on a limited budget finds his computer is running slowly. He uses his computer for university work and internet browsing.
Discuss what measures can be taken to improve Dan’s computer’s performance. You should explain what these measures are, why they improve the performance and justify whether you would recommend them.
- Replace CPU with faster CPU
- Add more/Faster RAM
- Add a graphics card
- Upgrade to faster secondary storage
(+more points)
The selected knowledge/examples should be directly related to the specific question and refer to their use + expenses to a university student
Defragmenting HDD is free and so should be performed.
Running anti-malware programs is free/low cost and should be done as a precaution against losing data anyway.
Moving to lighter weight software can potentially be free if the user considers open source software.
Compare a Complex Instruction Set Computer (CISC) architecture with a Reduced Instruction Set Computer (RISC) architecture.
CISC:
Each instruction may take multiple cycles
Single register set
Instructions have variable format
Many instructions are available
Many addressing modes are available
Complicated processor design
Integrated circuit is expensive
RISC:
An instruction performs a simple task
Limited number of instructions available
Complex tasks can only be performed by combining multiple instructions
Simple processor design
Explain one advantage, other than cost, of RISC compared with CISC
Programs run faster… …due to simpler instructions
Some computer systems use co-processors.
Explain the effect of using a co-processor system for each of the following applications.
(i) Complex calculations for scientific research.
Calculations are done by the maths co- processor…
…so processing is faster
…when using floating point arithmetic
