diff --git a/src/mame/drivers/segae.cpp b/src/mame/drivers/segae.cpp
index 55035533d26..0024c9d0501 100644
--- a/src/mame/drivers/segae.cpp
+++ b/src/mame/drivers/segae.cpp
@@ -995,7 +995,7 @@ static MACHINE_CONFIG_DERIVED( hangonjr, systeme )
 MACHINE_CONFIG_END
 
 static MACHINE_CONFIG_DERIVED( ridleofp, systeme )
-	MCFG_DEVICE_ADD("upd4701", UPD4701A, 0)
+	MCFG_DEVICE_ADD("upd4701", UPD4701A, 0) // on 834-6193 I/O sub board
 	MCFG_UPD4701_PORTX("PAD1")
 	MCFG_UPD4701_PORTY("PAD2")