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Different parts of instruction execution happen in different places:
- Control Unit - fetches, decodes, and distributes decoded instructions to other units.
- Arithmetic Logic Unit - performs arithmetic and logic instructions on command from Control Unit.
- Input/Output Unit(s) - performs input/output instructions on command from Control Unit.
- Memory Unit - stores instructions and data, transfers them to/from other units on command from Control Unit.
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What technology called a processor can begin executing an instruction before it completes the previous instruction?
The 8085 microprocessor does not prefetch instructions. The 8086/8088 and higher microprocessors do, in order to boost performance. They are trading idle time in the bus-interface unit, idle time waiting on the execution unit, in order to attempt to have the next instruction already fetched and available when the execution unit finally needs it. This is done by separating the execution unit from the bus-interface unit, and allowing them to operate somewhat asynchronously. Since most instructions will be followed by instructions at the next higher address, this can boost performance by minimizing idle time.
What are the four distinct actions that a machine instruction can specify?
• The processor fetches the instruction from memory • Program counter (PC) holds address of the instruction to be fetched next • PC is incremented after each fetch • Fetched instruction loaded into instruction register
What is meant by 'test and branch instruction'?
test and branch instruction
Which instruction set is used by the itaniums processors?
EPIC, which stands for Explicitly Parallel Instruction Computing.
What is address sequencing in computer organization?
Microinstructions are stored in control memory in groups, with each group specifying routine. Each computer instruction has its own microprogram routine in control memory to generate the microoperations that execute the instruction. The hardware that controls the address sequencing of the control memory must be capable of sequencing the microinstructions within a routine and be able to branch from one routine to another. To appreciate the address sequencing in a microprogram control unit, let us enumerate the steps that the control must undergo during the execution of a single computer instruction. An initial address is loaded into the control address register when power is turned on in the computer. This address is usually the address of the first microinstruction that activates the instruction fetch routine. The fetch routine may be sequenced by incrementing the control address register through the rest of its microinstructions. At the end of the fetch routine, the instruction is in the instruction register of the computer. The control memory next must go through the routine that determines the effective address of the operand. A machine instruction may have bits that specify various addressing modes, such as indirect address and index registers. The effective address computation routine in control memory can be reached through a branch microinstruction, which is conditioned on the status of the mode bits of the instruction. When the effective address computation routine is completed, the address of the operand is available in the memory address register. The next step is to generate the microoperations that execute the instruction fetched from memory. The microoperation steps to be generated in processor register depend on the operation code part of the instruction. Each instruction has its own microprogram routine stored in a given location of control memory. The transformation from the instruction code bits to an address in control memory where the routine is located is referred to as a mapping process. A mapping procedure is a rule that transforms the instruction code into a control memory address. Once the required routine is reached, the microinstructions that execute the instruction may be sequenced by incrementing the control address register, but sometimes the sequence of microoperations will depend on values of certain status bits in processor registers. Micro programs that employ subroutines will require an external register for storing the return address. Return addresses cannot be stored in ROM because the unit has no writing capability. When the execution of the instruction is completed, control must return to the fetch routine. This is accomplished by executing an unconditional branch microinstruction to the first address of the fetch routine. In summary, the address sequencing capabilities required in control memory are: 1. Incrementing of the control address register. 2. Unconditional branch or conditional branch, depending on statues bit conditions. 3. A mapping process from the bits of the instruction to an address for control memory. 4. A facility for subroutine call and return.
What is instruction execution?
The definition of instruction execution is the process of carrying out an instruction by a computer. This is what was formerly known as a command execution in DOS.
Does an interrupt actually interrupt the execution of an instruction at any time during the instruction execution cycle?
Yes , an interrupt actually interrupt the execution of an instruction at any time during the instruction execution cycle.AS there the execution takes in 4 t cycles and t3 to take up the data and the 4th cycle for execution,if there is an interruption then there will be an interruption any time in any instruction execution cycle.
What is instruction execution time In what unit is a computer speed measured?
about instruction execution time
What happens when halt instruction is executed?
The processor stops and goes to the halt state. If an interrupt occurs, it responds and then continues execution.
What is an instruction phase together with the execution phase called?
The instruction phase together with the execution phase is called a "Machine Cycle".
What are the different phases in instruction execution explain?
Instruction execution can be divided into five phases. These are Phase-I: INSTRUCTION FETCH (IF) II: INSTRUCTION DECODE & OPERAND FETCH (ID) III: EXECUTION (EX) V: MEMORY OPERATION (MEM) V: WRITE BACK (WB) - Regards, Subhradip Das
What will be the contents of PC after the execution of RST 4 Instruction?
20H
What is instruction cycle with interrupts?
The instruction cycle is the basic operation cycle in a computer. This is what will take in data, process it and execute as required.
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.
What happens after an execution?
DEATH.
What action is taken when the processor under execution is interrupted by TRAP in 8085MPU?
Processor serves the interrupt request after completing the execution of the current instruction.
