diff --git a/Changes.txt b/Changes.txt
index 0b3081d9c..9fa07beaf 100644
--- a/Changes.txt
+++ b/Changes.txt
@@ -22,6 +22,8 @@
 
   * Added option to start random ROM.
 
+  * Added option for automatic phosphor.
+
   * Enhanced Game Properties dialog for multigame ROMs.
 
   * Added 2nd UI theme and hotkey for toggling UI theme.
diff --git a/docs/graphics/options_video_tv.png b/docs/graphics/options_video_tv.png
index 4cdb07c82..a2a4fe98a 100644
Binary files a/docs/graphics/options_video_tv.png and b/docs/graphics/options_video_tv.png differ
diff --git a/docs/index.html b/docs/index.html
index d5f9978d7..b61627da9 100644
--- a/docs/index.html
+++ b/docs/index.html
@@ -1309,6 +1309,11 @@
       <td>Alt + 3</td>
       <td>Cmd + 3</td>
     </tr>
+    <tr>
+      <td><i>Increase</i> 'phosphor' enabling mode</td>
+      <td>Ctrl-Alt + P</td>
+      <td>Ctrl-Cmd + P</td>
+    </tr>
     <tr>
       <td>Toggle 'phosphor' mode</td>
       <td>Alt + P</td>
@@ -2921,11 +2926,11 @@
     </tr>
 
     <tr>
-      <td><pre>-tv.phosphor &lt;always|byrom&gt;</pre></td>
-      <td>Determine how phosphor mode is enabled. If 'always', then the
-        ROM properties entry is ignored, and phosphor mode is always turned
-        on. Otherwise, the ROM properties determine whether phosphor mode
-        is used for each ROM.
+      <td><pre>-tv.phosphor &lt;always|auto|byrom&gt;</pre></td>
+      <td>Determine how phosphor mode is enabled. If 'always' or 'auto', then
+        the ROM properties entry is ignored, and phosphor mode is either always
+        turned on or automatic. Otherwise, the ROM properties determine whether
+        phosphor mode is used for each ROM.
       </td>
     </tr>
 
@@ -3820,8 +3825,8 @@
           <tr><th>Item</th><th>Brief description</th><th>For more information,<br>see <a href="#CommandLine">Command Line</a></th></tr>
           <tr><td>TV mode</td><td>Disable TV effects, or select TV preset</td><td>-tv.filter</td></tr>
           <tr><td>Adjustable sliders</td><td>Set specific attribute in 'Custom' TV mode</td><td>-tv.sharpness<br/>-tv.resolution, etc.</td></tr>
-          <tr><td>Phosphor for all ROMs</td><td>Enable phosphor mode for all ROMs</td><td>-tv.phosphor</td></tr>
-          <tr><td>Blend (phosphor)</td><td>Blend level to use in phosphor mode for all ROMs
+          <tr><td>Phosphor</td><td>Select mode for enabling phosphor</td><td>-tv.phosphor</td></tr>
+          <tr><td>Blend (phosphor)</td><td>Blend level to use in phosphor modes for all ROMs and automatic
                 (needs to be manually adjusted for your particular hardware)</td><td>-tv.phosblend</td></tr>
           <tr><td>(Scanlines) Intensity</td><td>Sets scanlines black-level intensity.</br>
                   Note: No scanlines in 1x mode snapshots</td><td>-tv.scanlines</td></tr>
diff --git a/src/common/PKeyboardHandler.cxx b/src/common/PKeyboardHandler.cxx
index 74e10c0e1..b75d76fa0 100644
--- a/src/common/PKeyboardHandler.cxx
+++ b/src/common/PKeyboardHandler.cxx
@@ -660,6 +660,8 @@ PhysicalKeyboardHandler::DefaultCommonMapping = {
   { Event::PhosphorDecrease,         KBDK_4, KBDM_SHIFT | MOD3 },
   { Event::PhosphorIncrease,         KBDK_4, MOD3 },
   { Event::TogglePhosphor,           KBDK_P, MOD3 },
+  { Event::PhosphorModeDecrease,     KBDK_P, KBDM_SHIFT | KBDM_CTRL | MOD3 },
+  { Event::PhosphorModeIncrease,     KBDK_P, KBDM_CTRL | MOD3 },
   { Event::ScanlinesDecrease,        KBDK_5, KBDM_SHIFT | MOD3 },
   { Event::ScanlinesIncrease,        KBDK_5, MOD3 },
   { Event::PreviousScanlineMask,     KBDK_6, KBDM_SHIFT | MOD3 },
diff --git a/src/common/PhosphorHandler.cxx b/src/common/PhosphorHandler.cxx
index db31feb38..9b16c33f7 100644
--- a/src/common/PhosphorHandler.cxx
+++ b/src/common/PhosphorHandler.cxx
@@ -24,23 +24,24 @@ bool PhosphorHandler::initialize(bool enable, int blend)
     return false;
 
   myUsePhosphor = enable;
-  if(blend >= 0 && blend <= 100)
-    myPhosphorPercent = blend / 100.F;
-
-  // Used to calculate an averaged color for the 'phosphor' effect
-  const auto getPhosphor = [&] (const uInt8 c1, uInt8 c2) -> uInt8 {
-    // Use maximum of current and decayed previous values
-    c2 = static_cast<uInt8>(c2 * myPhosphorPercent);
-    if(c1 > c2)  return c1; // raise (assumed immediate)
-    else         return c2; // decay
-  };
 
   // Precalculate the average colors for the 'phosphor' effect
-  if(myUsePhosphor)
+  if((myUsePhosphor && blend != -1 && blend / 100.F != myPhosphorPercent) || !myLUTInitialized)
   {
+    if(blend >= 0 && blend <= 100)
+      myPhosphorPercent = blend / 100.F;
+
+    // Used to calculate an averaged color for the 'phosphor' effect
+    const auto getPhosphor = [&] (const uInt8 c1, uInt8 c2) -> uInt8 {
+      // Use maximum of current and decayed previous values
+      c2 = static_cast<uInt8>(c2 * myPhosphorPercent);
+      if(c1 > c2)  return c1; // raise (assumed immediate)
+      else         return c2; // decay
+    };
     for(int c = 255; c >= 0; --c)
       for(int p = 255; p >= 0; --p)
         ourPhosphorLUT[c][p] = getPhosphor(static_cast<uInt8>(c), static_cast<uInt8>(p));
+    myLUTInitialized = true;
   }
   return true;
 }
diff --git a/src/common/PhosphorHandler.hxx b/src/common/PhosphorHandler.hxx
index 7492c28d3..fbe3feb17 100644
--- a/src/common/PhosphorHandler.hxx
+++ b/src/common/PhosphorHandler.hxx
@@ -58,6 +58,7 @@ class PhosphorHandler
 
     // Amount to blend when using phosphor effect
     float myPhosphorPercent{0.50F};
+    bool myLUTInitialized{false};
 
     // Precalculated averaged phosphor colors
     using PhosphorLUT = BSPF::array2D<uInt8, kColor, kColor>;
diff --git a/src/common/jsonDefinitions.hxx b/src/common/jsonDefinitions.hxx
index 5be679942..e4c98991b 100644
--- a/src/common/jsonDefinitions.hxx
+++ b/src/common/jsonDefinitions.hxx
@@ -360,6 +360,8 @@ NLOHMANN_JSON_SERIALIZE_ENUM(Event::Type, {
   {Event::PhosphorDecrease, "PhosphorDecrease"},
   {Event::PhosphorIncrease, "PhosphorIncrease"},
   {Event::TogglePhosphor, "TogglePhosphor"},
+  {Event::PhosphorModeDecrease, "PhosphorModeDecrease"},
+  {Event::PhosphorModeIncrease, "PhosphorModeIncrease"},
   {Event::ToggleDeveloperSet, "ToggleDeveloperSet"},
   {Event::ToggleInter, "ToggleInter"},
   {Event::JitterSenseDecrease, "JitterSenseDecrease"},
diff --git a/src/emucore/Console.cxx b/src/emucore/Console.cxx
index a28657aae..ecc3e2d50 100644
--- a/src/emucore/Console.cxx
+++ b/src/emucore/Console.cxx
@@ -123,7 +123,17 @@ Console::Console(OSystem& osystem, unique_ptr<Cartridge>& cart,
   // Create subsystems for the console
   my6502 = make_unique<M6502>(myOSystem.settings());
   myRiot = make_unique<M6532>(*this, myOSystem.settings());
-  myTIA  = make_unique<TIA>(*this, [this]() { return timing(); },  myOSystem.settings());
+
+  const TIA::onPhosphorCallback callback = [&frameBuffer = this->myOSystem.frameBuffer()](bool enable)
+  {
+    frameBuffer.tiaSurface().enablePhosphor(enable);
+#if DEBUG_BUILD
+    ostringstream msg;
+    msg << "Phosphor effect automatically " << (enable ? "enabled" : "disabled");
+    frameBuffer.showTextMessage(msg.str());
+#endif
+  };
+  myTIA  = make_unique<TIA>(*this, [this]() { return timing(); }, myOSystem.settings(), callback);
   myFrameManager = make_unique<FrameManager>();
   mySwitches = make_unique<Switches>(myEvent, myProperties, myOSystem.settings());
 
@@ -615,18 +625,65 @@ void Console::changeSpeed(int direction)
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void Console::togglePhosphor()
 {
-  if(myOSystem.frameBuffer().tiaSurface().phosphorEnabled())
-  {
+  const bool enable = !myOSystem.frameBuffer().tiaSurface().phosphorEnabled();
+  if(!enable)
     myProperties.set(PropType::Display_Phosphor, "NO");
-    myOSystem.frameBuffer().tiaSurface().enablePhosphor(false);
-    myOSystem.frameBuffer().showTextMessage("Phosphor effect disabled");
-  }
   else
-  {
     myProperties.set(PropType::Display_Phosphor, "YES");
-    myOSystem.frameBuffer().tiaSurface().enablePhosphor(true);
-    myOSystem.frameBuffer().showTextMessage("Phosphor effect enabled");
+  myOSystem.frameBuffer().tiaSurface().enablePhosphor(enable);
+
+  // disable auto-phosphor
+  if(myTIA->autoPhosphorEnabled())
+    myTIA->enableAutoPhosphor(false);
+
+  ostringstream msg;
+  msg << "Phosphor effect " << (enable ? "enabled" : "disabled");
+  myOSystem.frameBuffer().showTextMessage(msg.str());
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void Console::cyclePhosphorMode(int direction)
+{
+  static constexpr std::array<string_view, 3> MESSAGES = {
+    "by ROM", "always on", "auto-enabled"
+  };
+  static constexpr std::array<string_view, 3> VALUE = {
+    "byrom", "always", "auto"
+  };
+  const string value = myOSystem.settings().getString("tv.phosphor");
+  int mode;
+
+  for(mode = 2; mode > 0; --mode)
+    if(value == VALUE[mode])
+      break;
+
+  if(direction)
+  {
+    mode = BSPF::clampw(mode + direction, 0, 2);
+    if(mode == 0)
+    {
+      myOSystem.frameBuffer().tiaSurface().enablePhosphor(
+        myProperties.get(PropType::Display_Phosphor) == "YES",
+        BSPF::stoi(myProperties.get(PropType::Display_PPBlend)));
+      myTIA->enableAutoPhosphor(false);
+    }
+    else if(mode == 1)
+    {
+      myOSystem.frameBuffer().tiaSurface().enablePhosphor(
+        true, myOSystem.settings().getInt("tv.phosblend"));
+      myTIA->enableAutoPhosphor(false);
+    }
+    else
+    {
+      myOSystem.frameBuffer().tiaSurface().enablePhosphor(
+        false, myOSystem.settings().getInt("tv.phosblend"));
+      myTIA->enableAutoPhosphor(true);
+    }
+    myOSystem.settings().setValue("tv.phosphor", VALUE[mode]);
   }
+  ostringstream msg;
+  msg << "Phosphor mode " << MESSAGES[mode];
+  myOSystem.frameBuffer().showTextMessage(msg.str());
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@@ -693,7 +750,7 @@ void Console::initializeAudio()
     .updateAudioQueueExtraFragments(myAudioSettings.bufferSize())
     .updateAudioQueueHeadroom(myAudioSettings.headroom())
     .updateSpeedFactor(myOSystem.settings().getBool("turbo")
-      ? 20.0F
+      ? 50.0F
       : myOSystem.settings().getFloat("speed"));
 
   createAudioQueue();
diff --git a/src/emucore/Console.hxx b/src/emucore/Console.hxx
index 6784805af..7ab8af4d8 100644
--- a/src/emucore/Console.hxx
+++ b/src/emucore/Console.hxx
@@ -252,6 +252,11 @@ class Console : public Serializable, public ConsoleIO
     */
     void togglePhosphor();
 
+    /**
+      Toggles auto-phosphor.
+    */
+    void cyclePhosphorMode(int direction = +1);
+
     /**
       Change the "Display.PPBlend" variable.
 
diff --git a/src/emucore/Event.hxx b/src/emucore/Event.hxx
index bd8573443..18d8ef939 100644
--- a/src/emucore/Event.hxx
+++ b/src/emucore/Event.hxx
@@ -115,7 +115,8 @@ class Event
       PreviousAttribute, NextAttribute, DecreaseAttribute, IncreaseAttribute,
       ScanlinesDecrease, ScanlinesIncrease,
       PreviousScanlineMask, NextScanlineMask,
-      PhosphorDecrease, PhosphorIncrease, TogglePhosphor, ToggleInter,
+      PhosphorDecrease, PhosphorIncrease, TogglePhosphor,
+      PhosphorModeDecrease, PhosphorModeIncrease, ToggleInter,
       ToggleDeveloperSet, JitterRecDecrease, JitterRecIncrease,
       JitterSenseDecrease, JitterSenseIncrease, ToggleJitter,
 
diff --git a/src/emucore/EventHandler.cxx b/src/emucore/EventHandler.cxx
index 7a32e9478..d1198a2f7 100644
--- a/src/emucore/EventHandler.cxx
+++ b/src/emucore/EventHandler.cxx
@@ -738,6 +738,22 @@ void EventHandler::handleEvent(Event::Type event, Int32 value, bool repeated)
       }
       return;
 
+    case Event::PhosphorModeDecrease:
+      if(pressed && !repeated)
+      {
+        myOSystem.console().cyclePhosphorMode(-1);
+        myGlobalKeyHandler->setSetting(GlobalKeyHandler::Setting::PHOSPHOR_MODE);
+      }
+      return;
+
+    case Event::PhosphorModeIncrease:
+      if(pressed && !repeated)
+      {
+        myOSystem.console().cyclePhosphorMode(+1);
+        myGlobalKeyHandler->setSetting(GlobalKeyHandler::Setting::PHOSPHOR_MODE);
+      }
+      return;
+
     case Event::ScanlinesDecrease:
       if(pressed)
       {
@@ -3004,6 +3020,8 @@ EventHandler::EmulActionList EventHandler::ourEmulActionList = { {
   { Event::IncreaseAttribute,       "Increase selected 'Custom' attribute"  },
   // Other TV effects
   { Event::TogglePhosphor,          "Toggle 'phosphor' effect"              },
+  { Event::PhosphorModeDecrease,    "Decrease 'phosphor' enabling mode"     },
+  { Event::PhosphorModeIncrease,    "Increase 'phosphor' enabling mode"     },
   { Event::PhosphorDecrease,        "Decrease 'phosphor' blend"             },
   { Event::PhosphorIncrease,        "Increase 'phosphor' blend"             },
   { Event::ScanlinesDecrease,       "Decrease scanlines"                    },
@@ -3181,6 +3199,7 @@ const Event::EventSet EventHandler::AudioVideoEvents = {
   Event::PreviousVideoMode, Event::NextVideoMode,
   Event::PreviousAttribute, Event::NextAttribute, Event::DecreaseAttribute, Event::IncreaseAttribute,
   Event::PhosphorDecrease, Event::PhosphorIncrease, Event::TogglePhosphor,
+  Event::PhosphorModeDecrease, Event::PhosphorModeIncrease,
   Event::ScanlinesDecrease, Event::ScanlinesIncrease,
   Event::PreviousScanlineMask, Event::NextScanlineMask,
   Event::ToggleInter,
diff --git a/src/emucore/EventHandler.hxx b/src/emucore/EventHandler.hxx
index c99dafb89..34beeb36b 100644
--- a/src/emucore/EventHandler.hxx
+++ b/src/emucore/EventHandler.hxx
@@ -540,7 +540,7 @@ class EventHandler
     #else
       REFRESH_SIZE         = 0,
     #endif
-      EMUL_ACTIONLIST_SIZE = 233 + PNG_SIZE + COMBO_SIZE + REFRESH_SIZE,
+      EMUL_ACTIONLIST_SIZE = 235 + PNG_SIZE + COMBO_SIZE + REFRESH_SIZE,
       MENU_ACTIONLIST_SIZE = 20
     ;
 
diff --git a/src/emucore/FrameBuffer.cxx b/src/emucore/FrameBuffer.cxx
index 3bbf1f434..95e27f0cd 100644
--- a/src/emucore/FrameBuffer.cxx
+++ b/src/emucore/FrameBuffer.cxx
@@ -328,12 +328,20 @@ FBInitStatus FrameBuffer::createDisplay(string_view title, BufferType type,
     // Phosphor mode can be enabled either globally or per-ROM
     int p_blend = 0;
     bool enable = false;
+    const string phosphor = myOSystem.settings().getString("tv.phosphor");
 
-    if(myOSystem.settings().getString("tv.phosphor") == "always")
+    myOSystem.console().tia().enableAutoPhosphor(phosphor == "auto");
+
+    if(phosphor == "always")
     {
       p_blend = myOSystem.settings().getInt("tv.phosblend");
       enable = true;
     }
+    else if(phosphor == "auto")
+    {
+      p_blend = myOSystem.settings().getInt("tv.phosblend");
+      enable = false;
+    }
     else
     {
       p_blend = BSPF::stoi(myOSystem.console().properties().get(PropType::Display_PPBlend));
@@ -719,7 +727,7 @@ void FrameBuffer::drawFrameStats(float framesPerSecond)
     << "fps @ "
     << std::fixed << std::setprecision(0) << 100 *
       (myOSystem.settings().getBool("turbo")
-        ? 20.0F
+        ? 50.0F
         : myOSystem.settings().getFloat("speed"))
     << "% speed";
 
diff --git a/src/emucore/GlobalKeyHandler.cxx b/src/emucore/GlobalKeyHandler.cxx
index 6c6874192..67355c43f 100644
--- a/src/emucore/GlobalKeyHandler.cxx
+++ b/src/emucore/GlobalKeyHandler.cxx
@@ -390,6 +390,7 @@ GlobalKeyHandler::SettingData GlobalKeyHandler::getSettingData(const Setting set
     {Setting::NTSC_BLEEDING,          {true,  std::bind(&TIASurface::changeNTSCAdjustable, &myOSystem.frameBuffer().tiaSurface(),
                                               static_cast<int>(NTSCFilter::Adjustables::BLEEDING), _1)}},
     // Other TV effects adjustables
+    {Setting::PHOSPHOR_MODE,          {true,  std::bind(&Console::cyclePhosphorMode, &myOSystem.console(), _1)}},
     {Setting::PHOSPHOR,               {true,  std::bind(&Console::changePhosphor, &myOSystem.console(), _1)}},
     {Setting::SCANLINES,              {true,  std::bind(&TIASurface::changeScanlineIntensity, &myOSystem.frameBuffer().tiaSurface(), _1)}},
     {Setting::SCANLINE_MASK,          {false, std::bind(&TIASurface::cycleScanlineMask, &myOSystem.frameBuffer().tiaSurface(), _1)}},
diff --git a/src/emucore/GlobalKeyHandler.hxx b/src/emucore/GlobalKeyHandler.hxx
index aef8c3b85..61ba7f91c 100644
--- a/src/emucore/GlobalKeyHandler.hxx
+++ b/src/emucore/GlobalKeyHandler.hxx
@@ -69,6 +69,7 @@ class GlobalKeyHandler
       NTSC_FRINGING,
       NTSC_BLEEDING,
       // Other TV effects adjustables
+      PHOSPHOR_MODE,
       PHOSPHOR,
       SCANLINES,
       SCANLINE_MASK,
diff --git a/src/emucore/ProfilingRunner.cxx b/src/emucore/ProfilingRunner.cxx
index 0c7229295..0adc1723f 100644
--- a/src/emucore/ProfilingRunner.cxx
+++ b/src/emucore/ProfilingRunner.cxx
@@ -125,7 +125,10 @@ bool ProfilingRunner::runOne(const ProfilingRun& run)
 
   M6502 cpu(mySettings);
   M6532 riot(consoleIO, mySettings);
-  TIA tia(consoleIO, []() { return ConsoleTiming::ntsc; }, mySettings);
+
+  const TIA::onPhosphorCallback callback = [] (bool enable) {};
+
+  TIA tia(consoleIO, []() { return ConsoleTiming::ntsc; }, mySettings, callback);
   System system(rng, cpu, riot, tia, *cartridge);
 
   consoleIO.myLeftControl = make_unique<Joystick>(Controller::Jack::Left, event, system);
diff --git a/src/emucore/Settings.cxx b/src/emucore/Settings.cxx
index 6b10dc991..0aeba5ed9 100644
--- a/src/emucore/Settings.cxx
+++ b/src/emucore/Settings.cxx
@@ -362,7 +362,7 @@ void Settings::validate()
   if(s != "bgopry")  setValue("tia.dbgcolors", "roygpb");
 
   s = getString("tv.phosphor");
-  if(s != "always" && s != "byrom")  setValue("tv.phosphor", "byrom");
+  if(s != "always" && s != "byrom" && s != "auto")  setValue("tv.phosphor", "byrom");
 
   i = getInt("tv.phosblend");
   if(i < 0 || i > 100)  setValue("tv.phosblend", "50");
@@ -576,7 +576,8 @@ void Settings::usage()
     << "  -tia.correct_aspect <1|0>     Enable aspect ratio correct scaling\n\n"
     << "  -tv.filter    <0-5>           Set TV effects off (0) or to specified mode\n"
     << "                                 (1-5)\n"
-    << "  -tv.phosphor  <always|byrom>  When to use phosphor mode\n"
+    << "  -tv.phosphor  <always|auto|>  When to use phosphor mode\n"
+    << "                 byrom\n"
     << "  -tv.phosblend <0-100>         Set default blend level in phosphor mode\n"
     << "  -tv.scanlines <0-100>         Set scanline intensity to percentage\n"
     << "                                 (0 disables completely)\n"
diff --git a/src/emucore/tia/TIA.cxx b/src/emucore/tia/TIA.cxx
index 78dcba927..795e10e0b 100644
--- a/src/emucore/tia/TIA.cxx
+++ b/src/emucore/tia/TIA.cxx
@@ -63,10 +63,11 @@ static constexpr uInt8 resxLateHblankThreshold = TIAConstants::H_CYCLES - 3;
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 TIA::TIA(ConsoleIO& console, const ConsoleTimingProvider& timingProvider,
-         Settings& settings)
+         Settings& settings, const onPhosphorCallback callback)
   : myConsole{console},
     myTimingProvider{timingProvider},
     mySettings{settings},
+    myPhosphorCallback{callback},
     myPlayfield{~CollisionMask::playfield & 0x7FFF},
     myMissile0{~CollisionMask::missile0 & 0x7FFF},
     myMissile1{~CollisionMask::missile1 & 0x7FFF},
@@ -186,6 +187,12 @@ void TIA::initialize()
   myFrontBuffer.fill(0);
   myFramebuffer.fill(0);
 
+  memset(&myPosP0, 0, sizeof(ObjectPos));
+  memset(&myPosP1, 0, sizeof(ObjectPos));
+  memset(&myPosM0, 0, sizeof(ObjectPos));
+  memset(&myPosM1, 0, sizeof(ObjectPos));
+  memset(&myPosBL, 0, sizeof(ObjectPos));
+
   applyDeveloperSettings();
 
   // Must be done last, after all other items have reset
@@ -193,6 +200,8 @@ void TIA::initialize()
   setFixedColorPalette(mySettings.getString("tia.dbgcolors"));
   enableFixedColors(
     mySettings.getBool(devSettings ? "dev.debugcolors" : "plr.debugcolors"));
+  myAutoPhosphorEnabled = mySettings.getString("tv.phosphor") == "auto";
+  myAutoPhosphorActive = false;
 
 #ifdef DEBUGGER_SUPPORT
   createAccessArrays();
@@ -1396,6 +1405,83 @@ void TIA::onFrameComplete()
 
   myFrontBufferScanlines = scanlinesLastFrame();
 
+  if(myAutoPhosphorEnabled)
+  {
+    static constexpr int MIN_FLICKER_DELTA = 6;
+    static constexpr int MAX_FLICKER_DELTA = TIAConstants::H_PIXEL - MIN_FLICKER_DELTA;
+    static constexpr int MIN_DIFF = 4;
+    static constexpr int PHOSPHOR_FRAMES = 8;
+
+    int diffCount[FLICKER_FRAMES - 1];
+
+    //cerr << missingScanlines << ", " << myFrontBufferScanlines << " | ";
+    //cerr << myFlickerFrame << ": ";
+    for(int frame = 0; frame < FLICKER_FRAMES - 1; ++frame)
+    {
+      int otherFrame = (myFlickerFrame + frame + 1) % FLICKER_FRAMES;
+      //cerr << otherFrame << " ";
+      // TODO:
+      // - differentiate fast movement and flicker
+      //   - movement is directional
+      //   - flicker goes back and forth
+      // - ignore disabled objects
+      diffCount[frame] = 0;
+      for(uInt32 y = 0; y < myFrontBufferScanlines; ++y)
+      {
+        int delta;
+        delta = std::abs(myPosP0[y][myFlickerFrame] - myPosP0[y][otherFrame]);
+        if(delta >= MIN_FLICKER_DELTA && delta <= MAX_FLICKER_DELTA)
+          ++diffCount[frame];
+        delta = std::abs(myPosP1[y][myFlickerFrame] - myPosP1[y][otherFrame]);
+        if(delta >= MIN_FLICKER_DELTA && delta <= MAX_FLICKER_DELTA)
+          ++diffCount[frame];
+        delta = std::abs(myPosM0[y][myFlickerFrame] - myPosM0[y][otherFrame]);
+        if(delta >= MIN_FLICKER_DELTA && delta <= MAX_FLICKER_DELTA)
+          ++diffCount[frame];
+        delta = std::abs(myPosM1[y][myFlickerFrame] - myPosM1[y][otherFrame]);
+        if(delta >= MIN_FLICKER_DELTA && delta <= MAX_FLICKER_DELTA)
+          ++diffCount[frame];
+        delta = std::abs(myPosBL[y][myFlickerFrame] - myPosBL[y][otherFrame]);
+        if(delta >= MIN_FLICKER_DELTA && delta <= MAX_FLICKER_DELTA)
+          ++diffCount[frame];
+      }
+    }
+    //cerr << ": ";
+    //for(int i = 0; i < FLICKER_FRAMES - 1; ++i)
+    //  cerr << diffCount[i] << ", ";
+    if(diffCount[0] > MIN_DIFF &&
+      (diffCount[0] > diffCount[1] * 1.1 ||
+       diffCount[0] > diffCount[2] * 1.2 ||
+       diffCount[0] > diffCount[3] * 1.3))
+    {
+      if(myFlickerCount < PHOSPHOR_FRAMES)
+      {
+        myFlickerCount += 2; // enabled phosphor twice as fast
+        if(myFlickerCount >= PHOSPHOR_FRAMES && !myAutoPhosphorActive)
+        {
+          myAutoPhosphorActive = true;
+          myPhosphorCallback(true);
+        }
+      }
+    }
+    else if(myFlickerCount)
+    {
+      if(--myFlickerCount == 0 && myAutoPhosphorActive)
+      {
+        myAutoPhosphorActive = false;
+        myPhosphorCallback(false);
+      }
+    }
+    //cerr << "|" << myFlickerCount;
+    //if(myAutoPhosphorActive)
+    //  cerr << " *** ON ***\n";
+    //else
+    //  cerr << " off\n";
+
+    if(--myFlickerFrame < 0)
+      myFlickerFrame = FLICKER_FRAMES - 1;
+  }
+
   ++myFramesSinceLastRender;
 }
 
@@ -1552,7 +1638,51 @@ FORCE_INLINE void TIA::nextLine()
   myBall.nextLine();
   myPlayfield.nextLine();
 
-  if (myFrameManager->isRendering() && myFrameManager->getY() == 0) flushLineCache();
+  if(myFrameManager->isRendering())
+  {
+    if(myFrameManager->getY() == 0)
+      flushLineCache();
+    if(myAutoPhosphorEnabled)
+    {
+      // Test ROMs:
+      // - missing phosphor:
+      //   x Princess Rescue: Lives display (~same x-position, different y-position)
+      //   - QB: flicker sprite for multi color (same position, different shape and color)
+      //   - Star Castle Arcade: vector font flicker (same position, different shape)
+      //   - Omega Race: no phosphor enabled (flickers every 2nd frame)
+      //   - Riddle of the Sphinx: shots (too small to be detected)
+      //   - Missile Command: explosions
+      //   - Yars' Revenge: shield, neutral zone (PF flicker)
+      //
+      // - unneccassary phosphor:
+      //   - Gas Hog: before game starts (odd invisible position changes)
+      //   x Turmoil: M1 rockets (gap between RESM1 and HMOVE?)
+      //   x Fathom: seaweed (many sprites moving vertically)
+      //   x FourPlay: game start (???)
+      //   x Freeway: always (too many sprites?)
+      const uInt32 y = myFrameManager->getY();
+      //const int otherFrame = myFlickerFrame ^ 1;
+      //cerr << y << " ";
+      //if(myPlayer0.getGRPOld() != 0)
+        myPosP0[y][myFlickerFrame] = myPlayer0.getPosition();
+      //if(myPlayer1.getGRPOld() != 0)
+        myPosP1[y][myFlickerFrame] = myPlayer1.getPosition();
+      //if(myMissile0.isOn())
+        myPosM0[y][myFlickerFrame] = myMissile0.getPosition();
+      //else
+      //  myPosM0[y][myFlickerFrame] = myPosM0[y][otherFrame];
+      //if(myMissile1.isOn())
+        myPosM1[y][myFlickerFrame] = myMissile1.getPosition();
+      //else
+      //  myPosM1[y][myFlickerFrame] = myPosM1[y][otherFrame];
+      //if(myBall.isOn())
+        myPosBL[y][myFlickerFrame] = myBall.getPosition();
+      //else
+      //  myPosBL[y][myFlickerFrame] = myPosBL[y][otherFrame];
+
+      //cerr << int(myPlayer0.getPosition()) << " ";
+    }
+  }
 
   mySystem->m6502().clearHaltRequest();
 }
@@ -1574,6 +1704,15 @@ void TIA::cloneLastLine()
 
     std::copy_n(myBackBuffer.begin() + (y - 1) * TIAConstants::H_PIXEL,
       TIAConstants::H_PIXEL, myBackBuffer.begin() + y * TIAConstants::H_PIXEL);
+
+    if(myAutoPhosphorEnabled)
+    {
+      myPosP0[y][myFlickerFrame] = myPosP0[y - 1][myFlickerFrame];
+      myPosP1[y][myFlickerFrame] = myPosP1[y - 1][myFlickerFrame];
+      myPosM0[y][myFlickerFrame] = myPosM0[y - 1][myFlickerFrame];
+      myPosM1[y][myFlickerFrame] = myPosM1[y - 1][myFlickerFrame];
+      myPosBL[y][myFlickerFrame] = myPosBL[y - 1][myFlickerFrame];
+    }
   }
 }
 
diff --git a/src/emucore/tia/TIA.hxx b/src/emucore/tia/TIA.hxx
index cb23147c8..811c80c64 100644
--- a/src/emucore/tia/TIA.hxx
+++ b/src/emucore/tia/TIA.hxx
@@ -109,6 +109,8 @@ class TIA : public Device
     friend class TIADebug;
     friend class RiotDebug;
 
+    using onPhosphorCallback = std::function<void(bool)>;
+
     /**
       Create a new TIA for the specified console
 
@@ -116,7 +118,7 @@ class TIA : public Device
       @param settings  The settings object for this TIA device
     */
     TIA(ConsoleIO& console, const ConsoleTimingProvider& timingProvider,
-        Settings& settings);
+        Settings& settings, const onPhosphorCallback callback);
     ~TIA() override = default;
 
   public:
@@ -277,6 +279,8 @@ class TIA : public Device
       Enables/disables color-loss for PAL modes only.
 
       @param enabled  Whether to enable or disable PAL color-loss mode
+
+      @return  True if color-loss got enabled
     */
     bool enableColorLoss(bool enabled);
 
@@ -294,6 +298,32 @@ class TIA : public Device
     */
     bool colorLossActive() const { return myColorLossActive; }
 
+    /**
+      Enables/disables auto-phosphor.
+
+      @param enabled  Whether to enable or disable auto-phosphor mode
+    */
+    void enableAutoPhosphor(bool enabled)
+    {
+      myAutoPhosphorEnabled = enabled;
+      if(!enabled)
+        myAutoPhosphorActive = false;
+    }
+
+    /**
+      Answers whether auto-phosphor is enabled.
+
+      @return  Auto-phosphor is enabled
+    */
+    bool autoPhosphorEnabled() const { return myAutoPhosphorEnabled; }
+
+    /**
+      Answers whether auto-phosphor is active.
+
+      @return  Auto-phosphor is acitve
+    */
+    bool autoPhosphorActive() const { return myAutoPhosphorActive; }
+
     /**
       Answers the current color clock we've gotten to on this scanline.
 
@@ -965,7 +995,17 @@ class TIA : public Device
     bool myColorLossEnabled{false};
     bool myColorLossActive{false};
 
-    std::array<uInt32, 16> myColorCounts;
+    /**
+    * Auto-phosphor detection variables.
+    */
+    bool myAutoPhosphorEnabled{true};
+    bool myAutoPhosphorActive{true};
+    static constexpr int FLICKER_FRAMES = 1 + 4; // compare current frame with previous 4 frames
+    using ObjectPos = BSPF::array2D<uInt8, TIAConstants::frameBufferHeight, FLICKER_FRAMES>;
+    ObjectPos myPosP0, myPosP1, myPosM0, myPosM1, myPosBL;
+    int myFlickerFrame{0};
+    int myFlickerCount{0};
+    onPhosphorCallback myPhosphorCallback;
 
   #ifdef DEBUGGER_SUPPORT
     /**
diff --git a/src/gui/GameInfoDialog.cxx b/src/gui/GameInfoDialog.cxx
index 7f2637ff2..e1bd070b7 100644
--- a/src/gui/GameInfoDialog.cxx
+++ b/src/gui/GameInfoDialog.cxx
@@ -160,7 +160,7 @@ void GameInfoDialog::addEmulationTab()
   // Phosphor
   ypos += lineHeight + VGAP;
   myPhosphor = new CheckboxWidget(myTab, _font, HBORDER, ypos + 1,
-                                  "Phosphor (enabled for all ROMs)", kPhosphorChanged);
+                                  "Phosphor (auto-enabled for all ROMs)", kPhosphorChanged);
   myPhosphor->setToolTip(Event::TogglePhosphor);
   wid.push_back(myPhosphor);
 
@@ -770,7 +770,6 @@ void GameInfoDialog::loadEmulationProperties(const Properties& props)
     }
   }
   myTypeDetected->setLabel(bsDetected);
-  updateMultiCart();
 
   // Start bank
   VarList::push_back(items, "Auto", "AUTO");
@@ -806,10 +805,13 @@ void GameInfoDialog::loadEmulationProperties(const Properties& props)
 
   // if phosphor is always enabled, disable game specific phosphor settings
   const bool alwaysPhosphor = instance().settings().getString("tv.phosphor") == "always";
+  const bool autoPhosphor = instance().settings().getString("tv.phosphor") == "auto";
   const bool usePhosphor = props.get(PropType::Display_Phosphor) == "YES";
   myPhosphor->setState(usePhosphor);
   if (alwaysPhosphor)
-    myPhosphor->setLabel("Phosphor (enabled for all ROMs)");
+    myPhosphor->setLabel("Phosphor (enabled for all ROMs");
+  else if (autoPhosphor)
+    myPhosphor->setLabel("Phosphor (auto-enabled for all ROMs)");
   else
     myPhosphor->setLabel("Phosphor");
 
@@ -823,6 +825,8 @@ void GameInfoDialog::loadEmulationProperties(const Properties& props)
   myVCenter->setValueUnit(vcenter ? "px" : "");
 
   mySound->setState(props.get(PropType::Cart_Sound) == "STEREO");
+
+  updateMultiCart();
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@@ -1191,9 +1195,9 @@ void GameInfoDialog::updateMultiCart()
   myFormat->setEnabled(!isMulti);
 
   // if phosphor is always enabled, disable game specific phosphor settings
-  const bool alwaysPhosphor = isMulti || instance().settings().getString("tv.phosphor") == "always";
-  myPhosphor->setEnabled(!alwaysPhosphor);
-  myPPBlend->setEnabled(!alwaysPhosphor && myPhosphor->getState());
+  const bool globalPhosphor = isMulti || instance().settings().getString("tv.phosphor") != "byrom";
+  myPhosphor->setEnabled(!globalPhosphor);
+  myPPBlend->setEnabled(!globalPhosphor && myPhosphor->getState());
 
   myVCenter->setEnabled(!isMulti);
   // if stereo is always enabled, disable game specific stereo setting
diff --git a/src/gui/VideoAudioDialog.cxx b/src/gui/VideoAudioDialog.cxx
index ef4926403..50b74ad6a 100644
--- a/src/gui/VideoAudioDialog.cxx
+++ b/src/gui/VideoAudioDialog.cxx
@@ -377,11 +377,17 @@ void VideoAudioDialog::addTVEffectsTab()
   CREATE_CUSTOM_SLIDERS(Bleed, "Bleeding ", 0)
 
   ypos += VGAP * 3;
-
   xpos = HBORDER;
 
   // TV Phosphor effect
-  myTVPhosphor = new CheckboxWidget(myTab, _font, xpos, ypos + 1, "Phosphor for all ROMs", kPhosphorChanged);
+  items.clear();
+  VarList::push_back(items, "by ROM", "byrom");
+  VarList::push_back(items, "always", "always");
+  VarList::push_back(items, "auto", "auto");
+  myTVPhosphor = new PopUpWidget(myTab, _font, xpos, ypos,
+                                 _font.getStringWidth("by ROM"), lineHeight,
+                                 items, "Phosphor ", 0, kPhosphorChanged);
+  myTVPhosphor->setToolTip(Event::PhosphorModeDecrease, Event::PhosphorModeIncrease);
   wid.push_back(myTVPhosphor);
   ypos += lineHeight + VGAP / 2;
 
@@ -754,7 +760,7 @@ void VideoAudioDialog::loadConfig()
   loadTVAdjustables(NTSCFilter::Preset::CUSTOM);
 
   // TV phosphor mode & blend
-  myTVPhosphor->setState(settings.getString("tv.phosphor") == "always");
+  myTVPhosphor->setSelected(settings.getString("tv.phosphor"), "byrom");
   myTVPhosLevel->setValue(settings.getInt("tv.phosblend"));
   handlePhosphorChange();
 
@@ -889,7 +895,7 @@ void VideoAudioDialog::saveConfig()
   NTSCFilter::saveConfig(settings);
 
   // TV phosphor mode & blend
-  settings.setValue("tv.phosphor", myTVPhosphor->getState() ? "always" : "byrom");
+  settings.setValue("tv.phosphor", myTVPhosphor->getSelectedTag());
   settings.setValue("tv.phosblend", myTVPhosLevel->getValueLabel() == "Off"
                                  ? "0" : myTVPhosLevel->getValueLabel());
 
@@ -1029,7 +1035,7 @@ void VideoAudioDialog::setDefaults()
       myTVMode->setSelected("0", "0");
 
       // TV phosphor mode & blend
-      myTVPhosphor->setState(false);
+      myTVPhosphor->setSelected("byrom");
       myTVPhosLevel->setValue(50);
 
       // TV scanline intensity & mask
@@ -1209,7 +1215,7 @@ void VideoAudioDialog::handleOverscanChange()
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void VideoAudioDialog::handlePhosphorChange()
 {
-  myTVPhosLevel->setEnabled(myTVPhosphor->getState());
+  myTVPhosLevel->setEnabled(myTVPhosphor->getSelectedTag() != "byrom");
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
diff --git a/src/gui/VideoAudioDialog.hxx b/src/gui/VideoAudioDialog.hxx
index 9f391f610..1b349e220 100644
--- a/src/gui/VideoAudioDialog.hxx
+++ b/src/gui/VideoAudioDialog.hxx
@@ -96,7 +96,7 @@ class VideoAudioDialog : public Dialog
     SliderWidget*     myTVBleed{nullptr};
 
     // TV phosphor effect
-    CheckboxWidget*   myTVPhosphor{nullptr};
+    PopUpWidget*      myTVPhosphor{nullptr};
     SliderWidget*     myTVPhosLevel{nullptr};
 
     // TV scanline intensity and interpolation