Pipeline Synchronization With The Nop Instruction - Motorola MC68030 User Manual

Instruction Set Summary
Another widely used application for bit field instructions is bit-mapped graphics. Because
byte boundaries are ignored in these areas of memory, the field definitions used with bit field
instructions are very helpful.

3.5.4 Pipeline Synchronization with the Nop Instruction

Although the no operation (NOP) instruction performs no visible operation, it serves an
important purpose. It forces synchronization of the integer unit pipeline by waiting for all
pending bus cycles to complete. All previous integer instructions and floating-point external
operand accesses complete execution before the NOP begins. The NOP instruction does
not synchronize the FPU pipeline; floating-point instructions with floating-point register
operand destinations can be executing when the NOP begins.
MOTOROLA MC68030 USER'S MANUAL 3-32