diff --git a/source/threads.tex b/source/threads.tex
index b3a041cf6f..6c6ccf472d 100644
--- a/source/threads.tex
+++ b/source/threads.tex
@@ -3011,6 +3011,30 @@
 \end{codeblock}
 \end{note}
 
+\pnum
+\begin{note}
+An implementation that
+translates to instruction sequences for a physical machine and
+treats non-volatile atomic accesses as though they were volatile
+does not produce out-of-thin-air values for a program free of undefined behavior.
+An implementation that
+performs only thread-at-a-time analysis in support of optimizations
+that omit and merge non-volatile atomic accesses to the same object and
+reorder non-volatile atomic accesses to different objects (when permitted by the as-if rule) and
+otherwise treats non-volatile atomic accesses as though they were volatile
+does not produce out-of-thin-air values for a program free of undefined behavior.
+The possibility of out-of-thin-air values remains
+for implementations not meeting these restrictions.
+\end{note}
+
+\pnum
+\begin{note}
+Unlike abstract machines,
+physical machines are subject to instruction-execution and information-transfer latencies.
+Physical machines carefully manage any speculative execution
+so as to avoid generating out-of-thin-air values at the hardware level.
+\end{note}
+
 \pnum
 Atomic read-modify-write operations shall always read the last value
 (in the modification order) written before the write associated with