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How does bus interface unit work with execution unit?
The execution unit execute the instruction while the bus interface unit do the fetching and shows the results as an output
How program and data memory fetches can be overlapped in a Harvard architecture?
In Harvard architecture, the program memory space is distinct from data memory space. Such architecture requiring two connections. It can perform instruction fetch ( from program memory ) and data memory fetch simultaneously , by adopting a pipelined instruction execution approach, as shown below. A typical instruction execution consists of performing Fetch instruction, Decode instruction, Fetch operands, execution operation , store results. Then, by adopting a pipelined approach, which is possible in Harvard architecture, it is evident that the instruction throughput increases by overlapping. It is simple to imagine that in the above case, if all the above states are executed "one after the other" , the execution time of the instruction will be longer than when it is pipelined.
How program and data memory fetches can be overlapped in Harvard architecture?
In Harvard architecture, the program memory space is distinct from data memory space. Such architecture requiring two connections. It can perform instruction fetch ( from program memory ) and data memory fetch simultaneously , by adopting a pipelined instruction execution approach, as shown below. A typical instruction execution consists of performing Fetch instruction, Decode instruction, Fetch operands, execution operation , store results. Then, by adopting a pipelined approach, which is possible in Harvard architecture, it is evident that the instruction throughput increases by overlapping. It is simple to imagine that in the above case, if all the above states are executed "one after the other" , the execution time of the instruction will be longer than when it is pipelined.
Is flag a part of execution unit?
Yes, the flag is part of the execution unit in a CPU. Flags are special bits used to indicate the status of the processor, such as the results of arithmetic operations (e.g., zero, carry, overflow). They play a crucial role in controlling the flow of execution by influencing decision-making processes, such as branching and conditional operations.
What are various types of operations required for instruction Explain each?
Instruction execution in a computer involves several key operations: Fetch: The CPU retrieves an instruction from memory, using the program counter to determine the address of the next instruction. Decode: The fetched instruction is then interpreted by the control unit to determine the required action and the operands involved. Execute: The actual operation (arithmetic, logic, or control) is performed by the ALU (Arithmetic Logic Unit) or other processing units. Write-back: The results of the execution are written back to memory or registers, updating the system's state for subsequent instructions.
How is instructions executed in latest generation computers?
typically dispatched to several independent different execution units, then the results are reordered into original instruction order, this is called superscalar. but there are several other systems too.
What are the four basic operations of a processor?
The four basic operations of a processor are fetch, decode, execute, and write back. During the fetch phase, the processor retrieves an instruction from memory. In the decode phase, it interprets the instruction to understand what actions are required. The execute phase involves carrying out the instruction, and in the write back phase, the processor updates the memory or registers with the results of the execution.
How compare instruction is used in 8085?
The compare and subtract instructions in the 8085 both subtract one operand from another, and set flags accordingly. The subtract instruction stores the result in the accumulator, while the compare instruction does not - except for the flags, the compare instruction "throws" the result away.
How does 8086 queue speeds up processing?
The instruction prefetch queue speeds up the processing of microprocessors by attempting to have the next opcode bytes available to the execution unit before it actually needs them. This works because, statistically, there is time spent by the execution unit in executing a particular instruction; time that the bus interface unit can use to go ahead and prefetch the next opcode bytes. Sometimes, this results in a loss of time, because the execution unit may branch to some other location. Modern processors attempt to sidestep that by using branch prediction algorithms.
Why pipelining used in 8086?
8086 is a pipelined processor. In 8086 to speed up the execution of a program,instruction fetching and executing the instruction are overlapped each other.This is a part of pipelined technique.
What are the flags affected after add instruction execution?
After the execution of an ADD instruction, the following flags in the processor's status register may be affected: the Zero Flag (ZF), which is set if the result is zero; the Sign Flag (SF), which indicates if the result is negative; the Carry Flag (CF), which is set if there is an overflow from the most significant bit; and the Overflow Flag (OF), which is set if the addition results in an overflow for signed integers. Additionally, the Parity Flag (PF) may also be updated based on the parity of the result.
Draw the functional block diagram of 8086 microprocessor and explain?
8086 has two blocks Bus Interfacing Unit(BIU) and Execution Unit(EU).The BIU performs all bus operations such as instruction fetching, reading and writing operands for memory and calculating the addresses of the memory operands. The instruction bytes are transferred to the instruction queue.EU executes instructions from the instruction system byte queue.Both units operate asynchronously to give the 8086 an overlapping instruction fetch and execution mechanism which is called as Pipelining. This results in efficient use of the system bus and system performance.BIU contains Instruction queue, Segment registers, Instruction pointer, Address adder.EU contains Control circuitry, Instruction decoder, ALU, Pointer and Index register,Flag register.
