Precise exception
Beginner
When something goes wrong in one step, the processor stops so that every earlier step is finished and no later step has changed anything.
Novice
An error or interrupt handled as if the processor stopped exactly between two instructions: everything before has completed and nothing after has had any effect. Out-of-order cores get this by retiring in order.
Expert
Required for demand paging and restartable faults. Implemented by recording exceptions in the ROB and acting on them only at commit, flushing all younger instructions.
Explained in Branch prediction and out-of-order execution (Architectures).
See also: Reorder buffer (ROB).