diff --git a/papers/format.md b/papers/format.md
index e0aa592f..f166d43e 100644
--- a/papers/format.md
+++ b/papers/format.md
@@ -290,6 +290,7 @@ size | description
      |   - 0xc8: SM8521 - 3 channels
      |   - 0xc9: M114S - 16 channels
      |   - 0xca: ZX Spectrum (beeper, QuadTone engine) - 5 channels
+     |   - 0xcb: Casio PV-1000 - 3 channels
      |   - 0xde: YM2610B extended - 19 channels
      |   - 0xe0: QSound - 19 channels
      |   - 0xfc: Pong - 1 channel
diff --git a/src/gui/presets.cpp b/src/gui/presets.cpp
index dd72ac3b..9d48dbf1 100644
--- a/src/gui/presets.cpp
+++ b/src/gui/presets.cpp
@@ -1111,7 +1111,7 @@ void FurnaceGUI::initSystemPresets() {
   ENTRY(
     "Commander X16", {
       CH(DIV_SYSTEM_VERA, 1.0f, 0, ""),
-      CH(DIV_SYSTEM_YM2151, 0.5f, 0, "")
+      CH(DIV_SYSTEM_YM2151, 1.0f, 0, "")
     }
   );
   ENTRY(
diff --git a/src/gui/tutorial.cpp b/src/gui/tutorial.cpp
index b8e04477..6741399e 100644
--- a/src/gui/tutorial.cpp
+++ b/src/gui/tutorial.cpp
@@ -245,7 +245,7 @@ void FurnaceGUI::drawTutorial() {
 
   // tutorial
   if (curTutorial>=0 && curTutorial<GUI_TUTORIAL_MAX) {
-    if (ImGui::Begin("Tutorial",NULL,ImGuiWindowFlags_NoResize|ImGuiWindowFlags_AlwaysAutoResize|ImGuiWindowFlags_NoTitleBar)) {
+    if (ImGui::Begin("Tutorial",NULL,ImGuiWindowFlags_NoResize|ImGuiWindowFlags_AlwaysAutoResize|ImGuiWindowFlags_NoTitleBar|ImGuiWindowFlags_NoDocking)) {
       FurnaceGUITutorialStep& step=tutorials[curTutorial].steps[curTutorialStep];
       ImGui::Dummy(ImVec2(400.0*dpiScale,1.0));
       ImGui::TextWrapped("%s",step.text);