8086/8088 instruction execution pipeline disconnection reason

8086/8088 Reason for instruction execution pipeline disconnection

1. There are transfer class instructions in the instruction prefetch queue

2. Executing an instruction requires parameters

When the execution of an instruction requires parameters （ such as ： Add ）,EU You have to get the parameters to execute the instruction smoothly , Therefore, the parallel pipeline is still disconnected .

3. The execution unit is slow

EU An instruction has not been executed yet ,BIU The prefetch queue in has been filled .

Function of bus interface unit

1. As CPU I / O interface with memory ;

2. Reading instructions from memory fills the instruction prefetch queue （ One instruction takes up two 8 Bit prefetch unit ）;

3. When a transfer class instruction is encountered , Clear the instruction prefetch queue and fetch the instruction again .