SLR1- Structure and Function of the Processor Flashcards
1
Q
What is the purpose of the Control Unit?
A
- Coordinates all activities of the CPU
- Directs flow of data between CPU and other devices
- Accepts the next instruction, decodes it, handles execution and stores data back in memory or registers.
- Sends read and write requests to main memory on the control bus, as well as other requests such as interrupt requests.
2
Q
What is the purpose of the Program Counter?
A
- Holds the address of the next instruction to be executed (could be next in sequence or address to jump to if current instruction is a jump or branch- copied from CIR)
- At the end of FDE cycle the address held in the PC is copied to the MAR
3
Q
What is the purpose of the MAR?
A
- Holds the address or memory location from which data or an instruction is to be fetched or to which data is to be written.
- Sends the address to memory down the address bus.
4
Q
What is the MDR used for?
A
- Used to temporarily store the data which is read from or written to memory.
- Sometimes known as the MBR (memory buffer register) also nicknamed the gateway to the processor.
- All data from memory must travel down the data bus and pass through the MDR
5
Q
What is the purpose of the Current Instruction Register?
A
- Holds the current instruction being executed.
- Contents of MDR are copied to CIR if it is an instruction.
- Contains the opcode and operand(s) of the current instruction
6
Q
What is the purpose of the Arithmetic Logic Unit?
A
- Performs arithmetic and logical operations on data.
- Arithmetic operations on fixed and floating point numbers
- ADD
- SUBTRACT
- MULTIPLY
- DIVIDE
- Bitwise shift operations left and right.
- Boolean logic operations
- AND
- OR
- NOT
- XOR
- Comparison
- Often uses general-purpose registers to store results of calculations such ass the accumulator
7
Q
What is the purpose of the Accumulator?
A
- One of many general-purpose registers.
- Data control info is often stored in them.
- Typically, the more general-purpose registers a processer has, the faster it may operate.
- Results of ALU calculations are often stored here.
8
Q
What is the purpose of the Address Bus?
A
- Carries memory addresses that identify where the data is being read from or written to.
9
Q
What is the purpose of the Data Bus?
A
- Carries the binary 1’s and 0’s that make up the actual information being transmitted around the computer
10
Q
What is the purpose of the Control Bus?
A
- Carries command and control signals to and from every other component of the CPU/Computer
11
Q
What is add in assembly code?
A
ADD
12
Q
What is subtract in assembly code?
A
SUB
13
Q
What is store in assembly code?
A
STA
14
Q
What is load in assembly code?
A
LDA
15
Q
What is branch always in assembly code?
A
BRA
16
Q
What is branch if zero in assembly code?
A
BRZ
17
Q
What is branch if positive in assembly code?
A
BRP
18
Q
What is input in assembly code?
A
INP
19
Q
What is output in assembly code?
A
OUT
20
Q
What is end program in assembly code?
A
HLT
21
Q
What is data location in assembly code?
A
DAT
22
Q
What happens during the fetch stage?
A
- Program counter is checked.
- Addressed store is then copied into the MAR
- Address is then sent along the address bus to main memory where it waits to receive a signal from the control bus.
- Control unit sends read signal along control bus.
- Contents in address send along the data bus to the MDR and copied to the CIR
- Program counter contents are incremented so that it points to the next address to be executed.
23
Q
What happens during the decode stage?
A
- Instruction held in CIR is decoded by decode unit.
24
Q
Parts of an instruction?
A
Opcode: what to do
Operand: what to do it to
25
What happens during the execute stage?
- Address is sent to the memory address register.
- Address sent down the address bus to main memory.
- Control unit sends command signal along control bus to main memory.
- Contents can then be sent along the data bus to the MDR
- Contents of MDR copied to CIR
26
How does a program branch?
- Value in the program counter is replaced with the content of the operand from the current instruction register.
- As program counter contents have been updated to a new memory location, the program can jump around memory.
27
How does a program branch?
- Value in the program counter is replaced with the content of the operand from the current instruction register.
- As program counter contents have been updated to a new memory location, the program can jump around memory.
28
What is clock speed measured in?
Hz
29
What does clock speed mean?
- Number of cycles per second.
30
What is the cache used for?
- Temporary storage of data and instructions being read to and written from.
- Located on or near the CPU
- Stores copies of recent data and instructions.
- Much quicker to access than main memory (RAM)
31
What factors affect the performance of the CPU?
- Clock Speed
- Cache Size
- Number of Cores (note: doubling the number of cores doesn't double the overall speed.)
32
Key features of Harvard architecture?
- Instructions and data 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.
33
Key features of Von Neumann architecture?
- Shared memory space for instructions and data.
- Instructions and data are stored in the same format.
- A single control unit or processor follows a linear fetch-decode-execute.
- One instruction at a time.
- Registers are used as fast access to instructions and data.
34
What are modern machine architectures known as?
- Contemporary
35
What is SIMD?
- Single Instruction Multiple Data
- Uses parallel processing.
36
What does parallel processing do?
- Carries out a single instruction on multiple pieces of data at the same time.
- Often used by graphical processors.
37
What is MIMD?
- Multiple Instructions Multiple Data
- Another type of processing that carries out multiple instructions on multiple pieces of data simultaneously.
38
What is Distributed Computing?
- Where multiple computers on a shared network each take on part of a bigger problem.
