Christian Vogt told us about OS21 in

http://curl.haxx.se/mail/lib-2008-04/0443.html

diff --git a/docs/INSTALL b/docs/INSTALL
index 87c7f3d2068fb8fc4eb4691f3caf9374027b42e8..006407a449c0c9cbf8fb74d18eb77008ad1247ea 100644 (file)
--- a/docs/INSTALL
+++ b/docs/INSTALL
@@ -790,7 +790,8 @@ PORTS
         - PowerPC Linux
         - PowerPC Mac OS 9
         - PowerPC Mac OS X
-        - SuperH4 Linux 2.6.X
+        - SH4 Linux 2.6.X
+        - SH4 OS21
         - SINIX-Z v5
         - Sparc Linux
         - Sparc Solaris 2.4, 2.5, 2.5.1, 2.6, 7, 8, 9, 10