Answer:
The call of instructions and data must be sequential, there can be no reordering of instructions but to allow reordering, a fence must be created.
Step-by-step explanation:
Sequential consistent memory model is able to use instructions when or before processing is done and after processing, so long as the instruction order is sequential.
This is similar to uploading a video on you-tube, the site immediately creates a page for the video even before the video is fully uploaded. Sent tweeter messages are seen by different people at different times, but the messages appear to be arranged sequentially.