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To speed up the program execution, the B.I.U fetches six instructions byte ahead of time from memory and stores in FIFO registers called "queue". Since EU and B.I.U are independent, the B.I.U fetches additional instruction, while EU decodes and executes a previously fetched instruction.
When the execution unit is ready for its next instruction, it simply reads the instruction from the queue. The main point here is that, fetching of the next instruction is overlapped with the execution of current instruction. This is called pipe lining
pipe lining saves time required for executing instructions. For example, if a multiplication operation is to be performed with its operands and registers, the microprocessor takes 100 clock-cycles, however, without pipe lining and with pipe lining, the number of clock cycles required to multiply two operands get relatively reduced. There are many instructions in 8086 microprocessor that require huge number of clock cycles. Thus, the prefetch queue becomes a circular part in enhancing the performance of the system.
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What is the use of insertion queue in 8086?
Maybe you mean the prefetch queue?
What is the size of the instruction queue in 8086?
In 8086 the instruction queue is 6 byte long. This is because even the longest 8086 instruction is 6 byte long. Thus it is possible to prefetch even the longest instruction in the instruction set.
What is queue status 8086?
queue of 8086 microprocessor is 6 bits
What is size of instruction queue of 8086?
6 bytes
What is the length of the instruction queue in 8086?
6 bytes
Why 8086 has 6 byte que?
Because that's how Intel designed it. They chose a 6 byte queue in the 8086 in order to optimize speed versus latency of the execution unit versus the bus interface unit. The decision for 6 bytes, as compared to 4 or 8 or some other number was a cost tradeoff and a recognition of the average mix of instruction execution cycle times in a typical processing thread.
Why Intel kept the name 8086?
in 8086, there is instruction queue of 6 byte. It is one of the reason behind giving name. 8086 was introducing pipeline architecture.
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 is size of instruction queue of 8086 fixed to 6 bytes?
An instruction queue is used in the 8086 to speed up the average time it takes to process an instruction. Some instructions are faster than the bus, while some are slower. If the CPU had to wait for all of the instructions, there would be gaps of time where the CPU is doing nothing. The queue helps to eliminate that gap by prefetching instructions in the hope that they will be ready for use when the CPU gets to them.
Describe the functions of the 8086 queue?
The 8086/8088 instruction queue is a buffer that holds opcode bytes that have been prefetched by the bus interface unit. This speeds up operations of the processor by helping to reduce fetch latency, i.e. to improve the probability that an opcode byte fetched by the processor is already available.
What is cache in 8086?
8086 is a small 4 or 6 byte instruction cache or queue that perfetched a few instructions before they were executed. In addition, the 8086 addressed 1M byte of memory, which is 16 times more than 8085. N.K.Jha narayankumarjha2010@gmail.com
What is pipeline. how it is achieved in 8086.discuss in brief?
In terms of computer language a pipeline is a set of data elements which are combined together and the yield or output of one element is taken as input for the other. In an 8086 microprocessor a bus used to execute data with help of 6-byte prefetch que.
