I added this template to GNU automake 1.3 config.guess. This is the
diff between the original.

--- config.guess	1998-06-30 13:03:32+09	1.2
+++ config.guess	1998-06-30 23:59:11+09
@@ -742,7 +742,7 @@
     news*:NEWS-OS:*:6*)
 	echo mips-sony-newsos6
 	exit 0 ;;
-    R3000:*System_V*:*:* | R4000:UNIX_SYSV:*:*)
+    R3000:*System_V*:*:* | R4000:UNIX_SYSV:*:* | R4000:UNIX_SV:*:*)
 	if [ -d /usr/nec ]; then
 	        echo mips-nec-sysv${UNAME_RELEASE}
 	else
