cpu/hwfreelunch: Add vacuum-gap transistors and wordsmith

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

2 files changed, 29 insertions, 13 deletions

diff --git a/bib/hw.bib b/bib/hw.bib
index 1cc6612f..7d4772f1 100644
--- a/bib/hw.bib
+++ b/bib/hw.bib
@@ -883,6 +883,15 @@ on Computer Architecture",
  lastchecked="November 13, 2016",
 }
 
+@article{JinWooHan2014VacuumGapTransistor,
+ author="Jin-Woo Han and Meyya Mayyappan",
+ Title="Introducing the Vacuum Transistor: A Device Made of Nothing",
+ Year="2014",
+ Month="June",
+ pages="??--??",
+ Journal="IEEE Spectrum",
+}
+
 @unpublished{MichaelJKelly2017DeviceLevel,
  Author="Michael J. Kelly",
  Title="How Might the Manufacturability of the Hardware at Device Level Impact on Exascale Computing?",
diff --git a/cpu/hwfreelunch.tex b/cpu/hwfreelunch.tex
index db8795f4..76f048f1 100644
--- a/cpu/hwfreelunch.tex
+++ b/cpu/hwfreelunch.tex
@@ -110,6 +110,14 @@ to communicate between a CPU and main memory.
 	up on electrodynamics.
 }\QuickQuizEnd
 
+In fact, Stephen Hawking is said to have claimed that semiconductor
+manufacturers have but two fundamental problems:
+\begin{enumerate*}[(1)]
+\item The finite speed of light and
+\item The atomic nature of matter~\cite{BryanGardiner2007}.
+\end{enumerate*}
+That is right, light is too slow and atoms are too big!!!
+
 There are nevertheless some technologies (both hardware and software)
 that might help improve matters:
 
@@ -126,18 +134,11 @@ Each of these is described in one of the following sections.
 \subsection{Novel Materials and Processes}
 \label{sec:cpu:Novel Materials and Processes}
 
-Stephen Hawking is said to have claimed that semiconductor manufacturers
-have but two fundamental problems:
-\begin{enumerate*}[(1)]
-\item The finite speed of light and
-\item The atomic nature of matter~\cite{BryanGardiner2007}.
-\end{enumerate*}
-That is right, light is too slow and atoms are too big!!!
-
-It is possible that semiconductor manufacturers are approaching the limits
-implied by this pair of laws of physics, but there are nevertheless a
-few avenues of research and development focused on working around these
-fundamental limits.
+It is possible that Stephen Hawking is right, and that semiconductor
+manufacturers are approaching the limits implied by the finite speed of
+light and the non-zero sizes of atoms.
+However, there are a few avenues of research and development focused on
+working around these fundamental laws of physics.
 
 One workaround for the atomic nature of matter are so-called
 ``high-K dielectric'' materials, which allow larger devices to mimic the
@@ -153,6 +154,9 @@ reliably in production semiconductor devices.
 Another proposed workaround is the ``quantum dot'' approach that
 allows much smaller device sizes, but which is still in the research
 stage.
+Yet another proposed workaround is to replace the atoms making up the
+base of a traditional transistor with a vacuum, resulting in the
+vacuum-gap transistor.
 
 One challenge is that many recent hardware-device-level breakthroughs
 require very tight control of which atoms are placed
@@ -209,6 +213,8 @@ long horizontal electrical connections (which are both slow and
 power hungry) can be replaced by short vertical electrical connections,
 which are both faster and more power efficient.
 
+If you cannot make light go faster, make your devices smaller!
+
 However, delays due to levels of clocked logic will not be decreased
 by 3D integration, and significant manufacturing, testing, power-supply,
 and heat-dissipation problems must be solved for 3D integration to
@@ -259,7 +265,8 @@ users to make the specialized hardware affordable.
 In part due to these sorts of economic considerations, specialized
 hardware has thus far appeared only for a few application areas,
 including graphics processing (GPUs), vector processors (MMX, SSE,
-and VMX instructions), and, to a lesser extent, encryption.
+and VMX instructions), and, to a lesser extent, encryption and
+compression.
 And even in these areas, it is not always easy to realize the expected
 performance gains, for example, due to thermal
 throttling~\cite{VladKrasnov2017SIMDfreqscale,DanielLemire2018SIMDfreqscale,TravisDowns2020SIMDfreqscale}.