+
+
+
+\subsection{Life Cycle of an Instruction}
+
+The diagram below shows an input dock for purposes of illustration:
+
+\begin{center}
+\epsfig{file=in,width=4in}\\
+{\it an input dock}
+\end{center}
+
+Note the mux on the path between {\tt EF} (epilogue fifo) and {\tt IF}
+(instruction fifo); this is known as ``the hatch''. The hatch has two
+states: sealed and unsealed. When the machine powers up, the hatch is
+unsealed; it is sealed by the {\tt tail} instruction and unsealed
+whenever the outer loop counter is set to zero (for any
+reason\footnote{this includes {\tt OLC} being decremented to zero, a
+ {\tt set} instruction, or the occurrence
+ of a torpedo}).
+
+When an instruction arrives at the epilogue fifo ({\tt EF}), it waits
+there until the hatch is in the unsealed state; the instruction then
+enters the instruction fifo. When an instruction emerges from the
+instruction fifo, it arrives at the ``on deck'' ({\tt OD}) stage,
+where it may execute.
+
+\begin{center}
+\epsfig{file=out,width=4in}\\
+{\it an output dock}
+\end{center}
+
+\subsubsection{Torpedoes}
+
+A token sent to an instruction destination is called a {\it torpedo}.
+When a torpedo arrives at the tail of {\tt EF}, it is deposited in a
+waiting area (not shown) rather than being enqueued into {\tt EF}.
+
+There is a latch (not shown) called the {\it torpedo acknowledgment path
+ latch} ({\tt TAPL}) which stores a path. When a torpedo is consumed
+(see section ``On Deck''), a token is sent along the path held in this
+latch.
+
+\subsection{Format of an Instruction}