diff --git a/src/engine/song.h b/src/engine/song.h
index 4709566a5..ae7306019 100644
--- a/src/engine/song.h
+++ b/src/engine/song.h
@@ -146,7 +146,7 @@ struct DivSong {
   //     - 0: Genesis NTSC (7.67MHz)
   //     - 1: Genesis PAL (7.61MHz)
   //     - 2: 8MHz
-  //     - 3: AtGames Genesis (???)
+  //     - 3: AtGames Genesis (6.13MHz)
   // - YM2151:
   //   - bit 0-1: clock rate
   //     - 0: 3.58MHz (NTSC)
diff --git a/src/gui/gui.cpp b/src/gui/gui.cpp
index 559f9a9ab..0d80508b9 100644
--- a/src/gui/gui.cpp
+++ b/src/gui/gui.cpp
@@ -5176,7 +5176,7 @@ bool FurnaceGUI::loop() {
                 if (ImGui::RadioButton("FM Towns (8MHz)",(flags&3)==2)) {
                   e->setSysFlags(i,(flags&0x80000000)|2);
                 }
-                if (ImGui::RadioButton("AtGames Genesis",(flags&3)==3)) {
+                if (ImGui::RadioButton("AtGames Genesis (6.13MHz)",(flags&3)==3)) {
                   e->setSysFlags(i,(flags&0x80000000)|3);
                 }
                 bool ladder=flags&0x80000000;