\documentclass[10pt]{article}
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\usepackage{epsfig}
\usepackage{color}
\usepackage{bytefield1}
\usepackage{wrapfig}
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\def\to{\ $\rightarrow$\ }

\def\docnum{AM33}

\author{
\normalsize{
\begin{tabular}{c}
\end{tabular}}
}

\title{\vspace{-1cm}The FleetTwo Dock}

\begin{document}

\maketitle

\begin{abstract}
Changes:

\begin{tabular}{rl}
\color{red}
12-Mar
\color{black}
& renamed loop+repeat to outer+inner (not in red) \\
& renamed {\tt Z} flag to {\tt L} flag (not in red) \\
& rewrote ``inner and outer loops'' section \\
& updated all diagrams \\
\color{black}
7-Mar
& Moved address bits to the LSB-side of a 37-bit instruction \\
& Added {\it micro-instruction} and {\it composite instruction} terms \\
& Removed the {\tt DL} field, added {\tt decrement} mode to {\tt loop} \\
& Created the {\tt Hold} field \\
& Changed how ReLooping works \\
& Removed {\tt clog}, {\tt unclog}, {\tt interrupt}, and {\tt massacre} \\
\end{tabular}
\end{abstract}

\vfill

\begin{center}
\epsfig{file=overview,width=1.5in}
\epsfig{file=indock,width=3in}
\end{center}

\pagebreak

\section{Overview of Fleet}

A Fleet processor consists of a {\it switch fabric} with several
functional units called {\it ships} connected to it.  At each
connection between a ship and the switch fabric lies a programmable
element known as the {\it dock}.

A {\it path} specifies a route through the switch fabric from a
particular {\it source} to a particular {\it destination}.  The
combination of a path and a single word {\it payload} is called a {\it packet}.  The
switch fabric carries packets from their sources to their
destinations.  Each dock has two destinations: one for {\it
  instructions} and one for {\it data}.  A Fleet is programmed by
depositing packets into the switch fabric; these packets' paths lead
them to the instruction destinations of the docks.

When a packet arrives at the instruction destination of a dock, it is
enqueued for execution.  Before the instruction executes, it may cause
the dock to wait for a packet to arrive at the dock's data destination
or for a value to be presented by the ship.  It may present a data
value to the ship or transmit it for transmission to some other
destination.

When an instruction sends a packet into the switch fabric, it may
specify that the payload of the packet is irrelevant.  Such packets
are known as {\it tokens}, and consume less energy than data packets.
From a programmer's perspective, a token packet is indistinguishable
from a data packet with a unknown payload.

\begin{center}
\epsfig{file=overview,width=3in}\\
\color{red}
{\it Overview of a Fleet processor; gray shading represents a
  packet-switched network fabric; blue lines carry data, red lines
  carry instructions.}
\end{center}
\color{black}

\pagebreak

\section{The FleetTwo Pump}

The diagram below represents a {\it programmer's} conceptual view of
the interface between ships and the switch fabric.  Actual
implementation circuitry may differ substantially.  Sources and
destinations that can send and receive only tokens -- not data items
-- are drawn as dashed lines.

\begin{center}
\epsfig{file=indock,width=3.5in}\\
{\it an ``input'' dock}

\epsfig{file=outdock,width=3.5in}\\
{\it an ``output'' dock}
\end{center}

The term {\it port} refers to an interface to the ship, the {\it
  dock} connecting it to the switch fabric, and the corresponding
sources and destinations on the switch fabric.

Each dock consists of a {\it data latch}, which is as wide as a single
machine word and a {\it pump}, which is a circular fifo of
instruction-width latches.  The values in the pump control the data
latch.

Note that the pump in each dock has a destination of its own; this is
the {\it instruction destination} mentioned in the previous section.
Note that unlike all other destinations, there is no buffering fifo
guarding this one.  The size of these fifos are exposed to the
software programmer so \color{red}he\color{black}\ can avoid deadlock.

\pagebreak
\section{Instructions}

In order to cause an instruction to execute, the programmer must first
cause that instruction word to arrive in the data latch of some output
dock.  For example, this might be the ``data read'' output dock of the
memory access ship or the output of a fifo ship.  Once an instruction
has arrived at this output dock, it is {\it dispatched} by sending it
to the {\it instruction port} of the dock at which it is to execute.

Each instruction is 26 bits long, which makes it possible for an
instruction and an 11-bit path to fit in a single word of memory.
This path is the path from the {\it dispatching} dock to the {\it
  executing} dock.

\setlength{\bitwidth}{3.5mm}
{\tt \footnotesize
\begin{bytefield}{37}
  \bitheader[b]{0,10,11,36}\\
  \bitbox{26}{instruction} 
  \bitbox{11}{dispatch path} 
\end{bytefield}}

{\bf Note:} the instruction encodings below are simply ``something to
shoot at'' and a sanity check to make sure we haven't overrun our bit
budget.  The final instruction encodings will probably be
different.

All instruction words have the following format:

\setlength{\bitwidth}{3.5mm}
{\tt \footnotesize
\begin{bytefield}{37}
  \bitheader[b]{0,10,11,36}\\
\color{black}
  \bitbox{1}{A} 
  \bitbox{1}{OL} 
  \bitbox{2}{P} 
\color{light}
  \bitbox[tbr]{22}{} 
  \bitbox{11}{dispatch path} 
\color{black}
\end{bytefield}}

Each instruction word is called a {\it micro instruction}.
Collections of one or more micro instruction are known as {\it
  composite instructions}.

\color{red}

The {\tt A} bit stands for {\tt Armor}\footnote{this is to be
  pronounced with a Boston accent (``AAHH-mir'')}.
The {\tt OL} bit indicates whether or not this instruction is part of
an outer loop.  Both of the preceding bits are explained in the next section.

\color{black}

The abbreviation {\tt P} stands for {\it predicate}; this is a two-bit
code that indicates if the instruction should be executed or ignored.



\pagebreak
\subsection{Life Cycle of an Instruction}
\color{red}
The diagram below shows an input dock for purposes of illustration
(behavior at an output dock is identical).

\begin{center}
\epsfig{file=indock,width=3in}\\
{\it an input dock}
\end{center}

Note the circle on the path between ``instr horn'' and ``instr 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 as described below.

When a non-{\tt torpedo} instruction arrives at the instruction horn,
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'' stage and starts two processes  {\it
  concurrently}:

\begin{itemize}
\item
{\bf Process \#1}\\
If the instruction has the {\tt OL} bit set and the value of {\tt OC}
is nonzero, this process will wait for the hatch to be {\it sealed}
and then enqueue a duplicate copy of the instruction into the instruction fifo.

\item
{\bf Process \#2}\\
If the value of {\tt OC} is zero and the instruction at on-deck is
{\it not} an {\tt setOuter} instruction whose {\tt OL} bit is cleared,
this process will unseal the hatch, set the {\it inner} loop counter
to zero, and terminate.

Otherwise, the instruction will execute one or more times, as
determined by the flags, predicate, and inner loop counter (see
below).  If the instruction's {\tt A}rmor bit is not
set\footnote{note: we need to say something about only {\tt send}
  instructions being {\tt torpedo}able}, each execution attempt will
be arbitrated against the arrival of a {\tt torpedo} instruction at
the instruction horn.  If the {\tt torpedo} wins, the {\it outer} loop
counter is set to zero and this process terminates immediately.
\end{itemize}

When both processes have completed, the on deck stage is vacated and
another instruction may enter it.

Note that when a {\tt torpedo} arrives at the instruction horn it will
wait there until on deck is occupied by an instruction whose {\tt
  A}rmor bit is {\it not set}, but it does {\it not} wait for the
hatch to be unsealed.

\color{black}

\subsection{Inner and Outer Loops}

\color{red}

Using the mechanisms described above, a programmer can perform two
types of loops: {\it inner} loops of only one instruction and {\it
  outer} loops of multiple instructions.  Inner loops may be nested
within an outer loop, but no other nesting of loops is allowed.  The
paths used by inner loops and outer loops are shown below:

\begin{center}
\begin{minipage}{2in}
\begin{center}
\epsfig{file=inner-loop,width=2in}\\
{\it inner loop (in red)}
\end{center}
\end{minipage}
\begin{minipage}{2in}
\begin{center}
\epsfig{file=outer-loop,width=2in}\\
{\it outer loop (in red)}
\end{center}
\end{minipage}
\end{center}

Each type of loop has a counter associated with it: the {\tt IC}
counter for inner loops and the {\tt OC} counter for outer loops.
The inner loop counter applies only to {\tt send} instructions; all
other instructions ignore the inner loop counter.  When a {\tt send}
instruction reaches the on deck position, it will execute at least
once; the number of times it executes after that is determined by the
inner loop counter.

The outer loop counter applies to all instructions {\it except} the
instruction {\tt setOuter} with {\tt OL=0}, because such instructions
are needed to reset the outer loop counter after it becomes zero.
However, {\tt setOuter} with {\tt OL} set to {\it one} is useful for
resetting the loop counter in the middle of the execution of a loop.

\color{black}

\subsection{Flags}

The pump has four flags: {\tt A}, {\tt B}, {\tt S}, {\tt L}.  Of
these four, only the first two may be modified directly by
instructions.

\begin{itemize}
\item The {\tt A} and {\tt B} flags are general-purpose flags which
      may be set and cleared by the programmer.

\item
\color{red}
 The {\tt L} flag, known as the {\it last} flag, is set whenever
      the value in the outer counter ({\tt OC}) is one,
\color{black}
 indicating
      that the dock is in the midst of the last iteration of an
      outer loop.  This flag can be used to perform certain
      operations (such as sending a completion token) only on the last
      iteration of an outer loop.

\item The {\tt S} flag, known as the {\it summary} flag.  Its value is
      determined by the ship, but unless stated otherwise, it should
      be assumed that whenever the 37th bit of the data ({\tt D})
      latch is loaded, that same bit is also loaded into the {\tt S}
      flag.  This lets the ship make decisions based on whether or not
      the top bit of the data latch is set; if two's complement
      numbers are in use, this will indicate whether or not the
      latched value is negative.
\end{itemize}

Many instruction fields are specified as two-bit {\it predicates}.
These fields contain one of four values, indicating if an action
should be taken unconditionally or conditionally on one of the {\tt A}
or {\tt B} flags:

\begin{itemize}
\item {\tt 00:} if {\tt A} is set
\item {\tt 10:} if {\tt B} is set
\item {\tt 01:} if {\tt L} is set ({\tt OC=1})
\item {\tt 11:} always
\end{itemize}


\pagebreak
\subsection{{\tt send} (variants: {\tt sendto}, {\tt dispatch})}

\setlength{\bitwidth}{5mm}
{\tt
\begin{bytefield}{26}
  \bitheader[b]{12-16,19,21}\\
\color{light}
  \bitbox{1}{A}
  \bitbox{1}{OL}
  \bitbox{2}{P}
\color{black}
   \bitbox{3}{001} 
\color{light}
  \bitbox[trb]{2}{} 
\color{black}
  \bitbox{1}{\tt Ti}
  \bitbox{1}{\tt Di}
  \bitbox{1}{\tt Dc}
  \bitbox{1}{\tt Do}
  \bitbox{1}{\tt To}
  \bitbox[l]{17}{}
\end{bytefield}}

%\begin{bytefield}{26}
%  \bitheader[b]{12-18}\\
%  \bitbox[]{8}{\raggedleft Input Dock:}
%  \bitbox[r]{2}{}
%  \bitbox{1}{\tt So} 
%  \bitbox{1}{\tt Dc}
%  \bitbox[l]{15}{}
%\end{bytefield}
%
%\begin{bytefield}{26}
%  \bitheader[b]{12-18}\\
%  \bitbox[]{8}{\raggedleft Output Dock:}
%  \bitbox[r]{2}{}
%  \bitbox{1}{\tt Si}
%  \bitbox{1}{\tt To}
%  \bitbox[l]{15}{}
%\end{bytefield}

\begin{bytefield}{26}
  \bitheader[b]{0,10,11}\\
  \bitbox[1]{13}{\raggedleft {\tt sendto} ({\tt LiteralPath\to Path})}
  \bitbox[r]{1}{}
  \bitbox{1}{\tt 1}
  \bitbox{11}{\tt LiteralPath}
\end{bytefield}

\begin{bytefield}{26}
  \bitheader[b]{10,11}\\
  \bitbox[1]{13}{\raggedleft {\tt dispatch} ({\tt DP[37:27]\to Path})\ \ }
  \bitbox[r]{1}{}
  \bitbox{1}{\tt 0}
  \bitbox{1}{\tt 1}
\color{light}
  \bitbox[trb]{10}{}
\color{black}
\end{bytefield}

\begin{bytefield}{26}
  \bitheader[b]{10,11}\\
  \bitbox[1]{13}{\raggedleft {\tt send} ({\tt Path} unchanged):}
  \bitbox[r]{1}{}
  \bitbox{1}{\tt 0}
  \bitbox{1}{\tt 0}
\color{light}
  \bitbox[trb]{10}{}
\color{black}
\end{bytefield}

\begin{itemize}
\item {\tt Ti} - Token Input: wait for the token predecessor to be full and drain it.
\item {\tt Di} - Data Input: wait for the data predecessor to be full and drain it.
\item {\tt Dc} - Data Capture: pulse the data latch.
\item {\tt Do} - Data Output: fill the data successor.
\item {\tt To} - Token Output: fill the token successor.
\end{itemize}

The data successor and token successor must both be empty in order for
a {\tt send} instruction to attempt execution.

The inner loop counter can hold a number {\tt 0..MAX} or a special
value $\infty$.  If {\tt IC} is nonzero after execution of a {\tt
  send} instruction, the instruction will execute again, and {\tt IC}
will be latched with {\tt (IC==$\infty$?$\infty$:max(IC-1, 0))}.  When
the inner loop counter reaches zero, the instruction ceases executing.


\pagebreak
\subsection{{\tt data}, {\tt datahi}, {\tt datalo}}

These instructions load part or all of the data latch ({\tt D}).

{\tt datahi: Literal[18:1]\to D[37:20]} (and {\tt Literal[18]\to S})

\setlength{\bitwidth}{5mm}
{\tt
\begin{bytefield}{26}
  \bitheader[b]{0,18,19,21}\\
\color{light}
  \bitbox{1}{A}
  \bitbox{1}{OL} 
  \bitbox{2}{P}
\color{black}
  \bitbox{1}{0} 
  \bitbox{2}{11} 
\color{light}
  \bitbox[trb]{1}{} 
\color{black}
  \bitbox{18}{Literal} 
\end{bytefield}}

{\tt datalo: Literal[19:1]\to D[19:1]}

\setlength{\bitwidth}{5mm}
{\tt
\begin{bytefield}{26}
  \bitheader[b]{0,18,19,21}\\
\color{light}
  \bitbox{1}{A}
  \bitbox{1}{OL} 
  \bitbox{2}{P}
\color{black}
  \bitbox{1}{0} 
  \bitbox{2}{10} 
  \bitbox{19}{Literal} 
\end{bytefield}}

{\tt data:}

\setlength{\bitwidth}{5mm}
{\tt
\begin{bytefield}{26}
  \bitheader[b]{0,18,19,21}\\
\color{light}
  \bitbox{1}{A}
  \bitbox{1}{OL} 
  \bitbox{2}{P}
\color{black}
  \bitbox{1}{1} 
  \bitbox{2}{SEL} 
  \bitbox{19}{Literal} 
\end{bytefield}}

{\tt
\begin{tabular}{|r|c|c|c|}\hline
sel  & D[37:20]      & D[19:1]       \\\hline
00  & Literal[18:1] & all 0         \\
01  & Literal[18:1] & all 1         \\
10  & all 0         & Literal[19:1] \\
11  & all 1         & Literal[19:1] \\
\hline
\end{tabular}}




\subsection{{\tt flags}}

\setlength{\bitwidth}{5mm}
{\tt
\begin{bytefield}{26}
  \bitheader[b]{0,7,8,15,16-19,21}\\
\color{light}
  \bitbox{1}{A}
  \bitbox{1}{OL} 
  \bitbox{2}{P}
\color{black}
  \bitbox{3}{000}
  \bitbox{1}{0}
  \bitbox{2}{00}
\color{black}
  \bitbox{8}{nextA}
  \bitbox{8}{nextB}
\end{bytefield}}

The {\tt P} field is a predicate; if it does not hold, the instruction
is ignored.  Otherwise the two flags ({\tt A} and {\tt B}) are updated
according to the {\tt nextA} and {\tt nextB} fields; each specifies
the new value as the logical {\tt OR} of zero or more inputs:

\begin{center}
{\tt
\begin{bytefield}{8}
  \bitheader[b]{0-7}\\
  \bitbox{1}{${\text{\tt A}}$}
  \bitbox{1}{$\overline{\text{\tt A}}$}
  \bitbox{1}{${\text{\tt B}}$}
  \bitbox{1}{$\overline{\text{\tt B}}$}
  \bitbox{1}{${\text{\tt S}}$}
  \bitbox{1}{$\overline{\text{\tt S}}$}
  \bitbox{1}{${\text{\tt L}}$}
  \bitbox{1}{$\overline{\text{\tt L}}$}
\end{bytefield}}
\end{center}

Each bit corresponds to one possible input; all inputs whose bits are
set are {\tt OR}ed together, and the resulting value is assigned to
the flag.  Note that if none of the bits are set, the value assigned
is zero.  Note also that it is possible to produce a {\tt 1} by {\tt
  OR}ing any flag with its complement.


\pagebreak

\subsection{{\tt setInner}}

This instruction loads the inner loop counter with either a literal
number, the special value $\infty$, or the contents of the {\tt data}
register.

\setlength{\bitwidth}{5mm}
{\tt
\begin{bytefield}{26}
  \bitheader[b]{16-19,21}\\
\color{light}
  \bitbox{1}{A}
  \bitbox{1}{OL} 
  \bitbox{2}{P}
\color{black}
  \bitbox{3}{000}
  \bitbox{1}{0}
  \bitbox{2}{01}
\color{light}
  \bitbox[tbr]{8}{}
  \bitbox[l]{8}{}
\color{black}
\end{bytefield}}\\

\begin{bytefield}{26}
  \bitbox[r]{18}{\raggedleft from data latch:\hspace{0.2cm}\ }
  \bitbox{2}{\tt 00}
\color{light}
  \bitbox[tbr]{6}{} 
\color{black}
\end{bytefield}

\begin{bytefield}{26}
  \bitheader[b]{0,5,6,7}\\
  \bitbox[r]{18}{\raggedleft from literal:\hspace{0.2cm}\ }
  \bitbox{2}{\tt 10}
  \bitbox{6}{\tt Literal} 
\end{bytefield}

\begin{bytefield}{26}
  \bitheader[b]{0,5,6,7}\\
  \bitbox[r]{18}{\raggedleft with $\infty$\ \ }
  \bitbox{2}{\tt 11} 
\color{light}
  \bitbox[tbr]{6}{} 
\color{black}
\end{bytefield}


\subsection{{\tt setOuter}}

This instruction loads the outer loop counter {\tt OC} with either
{\tt max(0,OC-1)}, a literal or the contents of the {\tt data}
register.

\setlength{\bitwidth}{5mm}
{\tt
\begin{bytefield}{26}
  \bitheader[b]{16-19,21,24}\\
\color{light}
  \bitbox{1}{A}
  \bitbox{1}{OL}
\color{light}
  \bitbox[tbr]{2}{P}
\color{black}
  \bitbox{3}{000}
  \bitbox{1}{0}
  \bitbox{2}{10}
\color{light}
  \bitbox[tbr]{9}{} 
  \bitbox[l]{7}{}
\color{black}
\end{bytefield}}\\

\begin{bytefield}{26}
  \bitbox[r]{19}{\raggedleft {\tt max(0,OC-1)}:\hspace{0.2cm}\ }
  \bitbox{2}{\tt 00} 
%\color{light}
  \bitbox[tbr]{5}{} 
%\color{black}
\color{black}
\end{bytefield}

\begin{bytefield}{26}
  \bitbox[r]{19}{\raggedleft from data latch:\hspace{0.2cm}\ }
  \bitbox{2}{\tt 01} 
\color{light}
  \bitbox[tbr]{5}{} 
\color{black}
\end{bytefield}

\begin{bytefield}{26}
  \bitheader[b]{0,5,6}\\
  \bitbox[r]{19}{\raggedleft from literal:\hspace{0.2cm}\ }
  \bitbox{1}{\tt 1} 
  \bitbox{6}{\tt Literal} 
\end{bytefield}

\pagebreak
\subsection{{\tt takeOuterLoopCounter}}

\setlength{\bitwidth}{5mm}
{\tt
\begin{bytefield}{26}
  \bitheader[b]{16-19,21}\\
\color{light}
  \bitbox{1}{A}
  \bitbox{1}{OL} 
  \bitbox{2}{P}
\color{black}
  \bitbox{3}{000}
  \bitbox{1}{0}
  \bitbox{2}{11}
\color{light}
  \bitbox[tbr]{16}{} 
\color{black}
\end{bytefield}}

This instruction copies the value in the outer loop counter {\tt OC}
into the least significant bits of the data latch and leaves all other
bits of the data latch unchanged.

\subsection{{\tt takeInnerLoopCounter}}

\setlength{\bitwidth}{5mm}
{\tt
\begin{bytefield}{26}
  \bitheader[b]{16-19,21}\\
\color{light}
  \bitbox{1}{A}
  \bitbox{1}{OL} 
  \bitbox{2}{P}
\color{black}
  \bitbox{3}{???}
  \bitbox{1}{?}
  \bitbox{2}{??}
\color{light}
  \bitbox[tbr]{16}{} 
\color{black}
\end{bytefield}}

This instruction copies the value in the inner loop counter {\tt IC}
into the least significant bits of the data latch and leaves all other
bits of the data latch unchanged.


\subsection{{\tt torpedo}}

\setlength{\bitwidth}{5mm}
{\tt
\begin{bytefield}{26}
  \bitheader[b]{0,5,16-19,21}\\
\color{light}
  \bitbox{4}{} 
\color{black}
  \bitbox{3}{000} 
  \bitbox{1}{1}
  \bitbox{2}{00}
\color{light}
  \bitbox[tbr]{16}{} 
\end{bytefield}}

\color{red}
When a {\tt torpedo} instruction reaches the instruction horn, it will
wait there until an instruction is on deck whose {\tt A}rmor bit is
not set.  The {\tt torpedo} will then cause ``Process \#2'' of the on
deck instruction to terminate and will set the outer loop counter to zero.

\subsection{{\tt tail}}

\setlength{\bitwidth}{5mm}
{\tt
\begin{bytefield}{26}
  \bitheader[b]{0,5,16-19,21}\\
\color{light}
  \bitbox{4}{} 
\color{black}
  \bitbox{3}{000} 
  \bitbox{1}{1}
  \bitbox{2}{01}
\color{light}
  \bitbox[tbr]{16}{} 
\end{bytefield}}

When a {\tt tail} instruction reaches {\tt IH}, it seals the hatch.
The {\tt tail} instruction does not enter the instruction fifo.

\color{black}


%\pagebreak
%\subsection{{\tt interrupt}}
%
%\setlength{\bitwidth}{5mm}
%{\tt
%\begin{bytefield}{26}
%  \bitheader[b]{0,5,16-19,21}\\
%\color{light}
%  \bitbox{4}{} 
%\color{black}
%  \bitbox{3}{000} 
%  \bitbox{1}{1}
%  \bitbox{2}{00}
%\color{light}
%  \bitbox[tbr]{16}{} 
%\end{bytefield}}
%
%When an {\tt interrupt} instruction reaches {\tt IH}, it will wait
%there for the {\tt OD} stage to be full with an instruction that has
%the {\tt IM} bit set.  When this occurs, the instruction at {\tt OD}
%{\it will not execute}, but {\it may reloop} if the conditions for
%relooping are met.
%\footnote{The ability to interrupt an instruction yet have it reloop is very
%useful for processing chunks of data with a fixed size header and/or
%footer and a variable length body.}
%
%
%\subsection{{\tt massacre}}
%
%\setlength{\bitwidth}{5mm}
%{\tt
%\begin{bytefield}{26}
%  \bitheader[b]{16-19,21}\\
%\color{light}
%  \bitbox{4}{} 
%\color{black}
%  \bitbox{3}{000} 
%  \bitbox{1}{1}
%  \bitbox{2}{01}
%\color{light}
%  \bitbox[tbr]{16}{} 
%\color{black}
%\end{bytefield}}
%
%When a {\tt massacre} instruction reaches {\tt IH}, it will wait there
%for the {\tt OD} stage to be full with an instruction that has the
%{\tt IM} bit set.  When this occurs, all instructions in the
%instruction fifo (including {\tt OD}) are retired.
%
%\subsection{{\tt clog}}
%
%\setlength{\bitwidth}{5mm}
%{\tt
%\begin{bytefield}{26}
%  \bitheader[b]{16-19,21}\\
%\color{light}
%  \bitbox{4}{} 
%\color{black}
%  \bitbox{3}{000} 
%  \bitbox{1}{1}
%  \bitbox{2}{10}
%\color{light}
%  \bitbox[tbr]{16}{} 
%\color{black}
%\end{bytefield}}
%
%When a {\tt clog} instruction reaches {\tt OD}, it remains there and
%no more instructions will be executed until an {\tt unclog} is
%performed.
%
%\subsection{{\tt unclog}}
%
%\setlength{\bitwidth}{5mm}
%{\tt
%\begin{bytefield}{26}
%  \bitheader[b]{16-19,21}\\
%\color{light}
%  \bitbox{4}{} 
%\color{black}
%  \bitbox{3}{000} 
%  \bitbox{1}{1}
%  \bitbox[lrtb]{2}{11}
%\color{light}
%  \bitbox[tbr]{16}{} 
%\color{black}
%\end{bytefield}}
%
%When an {\tt unclog} instruction reaches {\tt IH}, it will wait there
%until a {\tt clog} instruction is at {\tt OD}.  When this occurs, both
%instructions retire.
%
%Note that issuing an {\tt unclog} instruction to a dock which is not
%clogged and whose instruction fifo contains no {\tt clog} instructions
%will cause the dock to deadlock.



\pagebreak
\epsfig{file=overview,height=5in,angle=90}

\pagebreak
\subsection*{Input Dock}
\epsfig{file=indock,width=7in,angle=90}

\pagebreak
\subsection*{Output Dock}
\epsfig{file=outdock,width=6.5in,angle=90}


%\pagebreak
%\epsfig{file=ports,height=5in,angle=90}

%\pagebreak
%\epsfig{file=best,height=5in,angle=90}


\end{document}
