diff --git a/share/man/man7/arch.7 b/share/man/man7/arch.7
index aef56898286..4ef89b59aae 100644
--- a/share/man/man7/arch.7
+++ b/share/man/man7/arch.7
@@ -333,6 +333,10 @@ or an external toolchain compiler and linker provided by a port or package.
 .El
 .Pp
 (1) External toolchain provided by ports/packages.
+.Pp
+Note that GCC 4.2.1 is deprecated, and scheduled for removal on 2020-03-31.
+CPU architectures not migrated to either base system Clang or external
+toolchain by then will be desupported.
 .Ss Predefined Macros
 The compiler provides a number of predefined macros.
 Some of these provide architecture-specific details and are explained below.