diff --git a/Changes.txt b/Changes.txt
index 3dc2b695f..87e470ba5 100644
--- a/Changes.txt
+++ b/Changes.txt
@@ -50,6 +50,8 @@
 
   * Fixed broken 7800 pause key support.
 
+  * Added developer option for random hotspot peek values.
+
   * Added user defined CPU cycle timers to debugger.
 
   * Removed 'launcherroms' option, since it was causing some issues.
diff --git a/docs/graphics/options_developer.png b/docs/graphics/options_developer.png
index 6a8525a65..95460ab06 100644
Binary files a/docs/graphics/options_developer.png and b/docs/graphics/options_developer.png differ
diff --git a/docs/graphics/options_developer_emulation.png b/docs/graphics/options_developer_emulation.png
index 1190c876d..f846843bf 100644
Binary files a/docs/graphics/options_developer_emulation.png and b/docs/graphics/options_developer_emulation.png differ
diff --git a/docs/index.html b/docs/index.html
index acd6c8a5d..f6aed096b 100644
--- a/docs/index.html
+++ b/docs/index.html
@@ -3640,6 +3640,9 @@
     </tr><tr>
       <td><pre>-&lt;plr.|dev.&gt;cpurandom &lt;S,A,X,Y,P&gt;</pre></td>
       <td>On reset, randomize the content of the specified CPU registers.</td>
+    </tr><tr>
+      <td><pre>-dev.hsrandom &lt;1|0&gt;</pre></td>
+      <td>When this option is enabled, peeks to hotspots return semi-random values.</td>
     </tr><tr>
       <td><pre>-dev.tiadriven &lt;1|0&gt;</pre></td>
       <td>Set unused TIA pins to be randomly driven high or low on a read/peek.
@@ -4567,6 +4570,11 @@
             <td>When loading a ROM, randomize the content of the specified CPU registers</td>
             <td>-plr.cpurandom<br/>-dev.cpurandom</td>
           </tr>
+          <tr>
+            <td>Random hotspot peek values</td>
+            <td>Peeks to hotspots return semi-random values</td>
+            <td>-dev.hsrandom</td>
+          </tr>
           <tr>
             <td>Drive unused TIA pins ...</td>
             <td>Unused TIA pins are read random instead of the last databus values</td>
diff --git a/src/common/DevSettingsHandler.cxx b/src/common/DevSettingsHandler.cxx
index e816076aa..bd9702f74 100644
--- a/src/common/DevSettingsHandler.cxx
+++ b/src/common/DevSettingsHandler.cxx
@@ -23,6 +23,7 @@
 #include "Settings.hxx"
 #include "StateManager.hxx"
 #include "TIA.hxx"
+#include "Cart.hxx"
 
 #include "DevSettingsHandler.hxx"
 
@@ -47,6 +48,8 @@ void DevSettingsHandler::loadSettings(SettingsSet set)
   myRandomizeTIA[set] = settings.getBool(prefix + "tiarandom");
   myRandomizeRAM[set] = settings.getBool(prefix + "ramrandom");
   myRandomizeCPU[set] = settings.getString(prefix + "cpurandom");
+  // Random hotspot peeks
+  myRandomHotspots[set] = devSettings ? settings.getBool("dev.hsrandom") : false;
   // Undriven TIA pins
   myUndrivenPins[set] = devSettings ? settings.getBool("dev.tiadriven") : false;
 #ifdef DEBUGGER_SUPPORT
@@ -110,6 +113,7 @@ void DevSettingsHandler::saveSettings(SettingsSet set)
 
   if(devSettings)
   {
+    settings.setValue("dev.hsrandom", myRandomHotspots[set]);
     // Undriven TIA pins
     settings.setValue("dev.tiadriven", myUndrivenPins[set]);
   #ifdef DEBUGGER_SUPPORT
@@ -168,6 +172,7 @@ void DevSettingsHandler::applySettings(SettingsSet set)
 
   if(myOSystem.hasConsole())
   {
+    myOSystem.console().cartridge().enableRandomHotspots(myRandomHotspots[set]);
     myOSystem.console().tia().driveUnusedPinsRandom(myUndrivenPins[set]);
     // Notes:
     // - thumb exceptions not updated, because set in cart constructor
diff --git a/src/common/DevSettingsHandler.hxx b/src/common/DevSettingsHandler.hxx
index b3b324bd7..365d8c28d 100644
--- a/src/common/DevSettingsHandler.hxx
+++ b/src/common/DevSettingsHandler.hxx
@@ -58,6 +58,7 @@ class DevSettingsHandler
     std::array<int, numSets>    myTVJitterSense;
     std::array<int, numSets>    myTVJitterRec;
     std::array<bool, numSets>   myDebugColors;
+    std::array<bool, numSets>   myRandomHotspots;
     std::array<bool, numSets>   myUndrivenPins;
   #ifdef DEBUGGER_SUPPORT
     std::array<bool, numSets>   myRWPortBreak;
diff --git a/src/common/PKeyboardHandler.cxx b/src/common/PKeyboardHandler.cxx
index cb85ec514..0b171ed36 100644
--- a/src/common/PKeyboardHandler.cxx
+++ b/src/common/PKeyboardHandler.cxx
@@ -70,8 +70,25 @@ PhysicalKeyboardHandler::PhysicalKeyboardHandler(OSystem& system, EventHandler&
 #ifdef DEBUGGER_SUPPORT
   setDefaultMapping(Event::NoType, EventMode::kPromptMode, updateDefaults);
 #endif
+#ifdef DEBUG_BUILD
+  verifyDefaultMapping(DefaultCommonMapping, EventMode::kEmulationMode, "EmulationMode");
+  verifyDefaultMapping(DefaultMenuMapping, EventMode::kMenuMode, "MenuMode");
+#endif
 }
 
+#ifdef DEBUG_BUILD
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void PhysicalKeyboardHandler::verifyDefaultMapping(
+  PhysicalKeyboardHandler::EventMappingArray mapping, EventMode mode, string_view name)
+{
+  for(const auto& item1 : mapping)
+    for(const auto& item2 : mapping)
+      if(item1.event != item2.event && item1.key == item2.key && item1.mod == item2.mod)
+        cerr << "ERROR! Duplicate hotkey mapping found: " << name << ", "
+          << myKeyMap.getDesc(KeyMap::Mapping(mode, item1.key, item1.mod)) << "\n";
+}
+#endif
+
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void PhysicalKeyboardHandler::loadSerializedMappings(
     string_view serializedMapping, EventMode mode)
@@ -660,6 +677,7 @@ 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 },
diff --git a/src/common/PKeyboardHandler.hxx b/src/common/PKeyboardHandler.hxx
index 7cdf5b247..2b3969afe 100644
--- a/src/common/PKeyboardHandler.hxx
+++ b/src/common/PKeyboardHandler.hxx
@@ -124,6 +124,11 @@ class PhysicalKeyboardHandler
     /** return event mode for given controller type */
     static EventMode getMode(const Controller::Type type);
 
+#ifdef DEBUG_BUILD
+    void verifyDefaultMapping(PhysicalKeyboardHandler::EventMappingArray mapping,
+      EventMode mode, string_view name);
+#endif
+
   private:
     OSystem& myOSystem;
     EventHandler& myHandler;
diff --git a/src/emucore/Cart.cxx b/src/emucore/Cart.cxx
index bd91358e3..3c98e1c93 100644
--- a/src/emucore/Cart.cxx
+++ b/src/emucore/Cart.cxx
@@ -37,6 +37,8 @@ Cartridge::Cartridge(const Settings& settings, string_view md5)
   for(uInt32 i = 0; i < 256; ++i)
     myRWPRandomValues[i] = rand.next();
 
+  const bool devSettings = mySettings.getBool("dev.settings");
+  myRandomHotspots = devSettings ? mySettings.getBool("dev.randomhs") : false;
   myRamReadAccesses.reserve(5);
 }
 
diff --git a/src/emucore/Cart.hxx b/src/emucore/Cart.hxx
index 2e031b8be..a859631b5 100644
--- a/src/emucore/Cart.hxx
+++ b/src/emucore/Cart.hxx
@@ -90,6 +90,8 @@ class Cartridge : public Device
     void unlockHotspots() { myHotspotsLocked = false; }
     bool hotspotsLocked() const { return myHotspotsLocked; }
 
+    void enableRandomHotspots(bool enable) { myRandomHotspots = enable; }
+
     /**
       Get the default startup bank for a cart.  This is the bank where
       the system will look at address 0xFFFC to determine where to
@@ -437,6 +439,9 @@ class Cartridge : public Device
     // Semi-random values to use when a read from write port occurs
     std::array<uInt8, 256> myRWPRandomValues;
 
+    // If myRandomHotspots is true, peeks to hotspots return semi-random values.
+    bool myRandomHotspots{false};
+
   private:
     // The startup bank to use (where to look for the reset vector address)
     uInt16 myStartBank{0};
diff --git a/src/emucore/CartEnhanced.cxx b/src/emucore/CartEnhanced.cxx
index 4cdbd9d50..0fd9c476d 100644
--- a/src/emucore/CartEnhanced.cxx
+++ b/src/emucore/CartEnhanced.cxx
@@ -161,7 +161,7 @@ uInt8 CartridgeEnhanced::peek(uInt16 address)
 
   // hotspots in TIA range are reacting to pokes only
   if(hotspot() >= 0x80)
-    if(checkSwitchBank(address & ADDR_MASK, 0))
+    if(checkSwitchBank(address & ADDR_MASK, 0) && myRandomHotspots)
       return myRWPRandomValues[address & 0xFF];
 
   if(isRamBank(address))
diff --git a/src/emucore/CartFA.cxx b/src/emucore/CartFA.cxx
index 6062e6941..f207da0dd 100644
--- a/src/emucore/CartFA.cxx
+++ b/src/emucore/CartFA.cxx
@@ -15,6 +15,7 @@
 // this file, and for a DISCLAIMER OF ALL WARRANTIES.
 //============================================================================
 
+#include "System.hxx"
 #include "CartFA.hxx"
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@@ -30,8 +31,10 @@ CartridgeFA::CartridgeFA(const ByteBuffer& image, size_t size,
 bool CartridgeFA::checkSwitchBank(uInt16 address, uInt8)
 {
   // Switch banks if necessary
-  if((address >= 0x1FF8) && (address <= 0x1FFA))
+  if((address >= 0x1FF8) && (address <= 0x1FFA)/* && (mySystem->getDataBusState() & 1) */)
   {
+    //if((mySystem->getDataBusState() & 1) == 0)
+    //cerr << std::hex << address << ": " << (mySystem->getDataBusState() & 1) << ", ";
     bank(address - 0x1FF8);
     return true;
   }
diff --git a/src/emucore/CartFA.hxx b/src/emucore/CartFA.hxx
index 503b3c8f5..67306c725 100644
--- a/src/emucore/CartFA.hxx
+++ b/src/emucore/CartFA.hxx
@@ -26,7 +26,8 @@
 
 /**
   Cartridge class used for CBS' RAM Plus cartridges.  There are three 4K
-  banks, accessible by read/write at $1FF8 - $1FFA, and 256 bytes of RAM.
+  banks, accessible by read/write at $1FF8 - $1FFA (note: D0 has to be 1
+  for switching), and 256 bytes of RAM.
   RAM read port is $1100 - $11FF, write port is $1000 - $10FF.
 
   @author  Bradford W. Mott, Thomas Jentzsch
diff --git a/src/emucore/Settings.cxx b/src/emucore/Settings.cxx
index 00bcbff3a..cdafa49b4 100644
--- a/src/emucore/Settings.cxx
+++ b/src/emucore/Settings.cxx
@@ -278,6 +278,7 @@ Settings::Settings()
   setPermanent("dev.ramrandom", "true");
   setPermanent("dev.cpurandom", "SAXYP");
   setPermanent("dev.tiarandom", "true");
+  setPermanent("dev.hsrandom", "true");
   setPermanent("dev.colorloss", "true");
 #ifdef GUI_SUPPORT
   setPermanent("dev.tv.jitter", "true");
@@ -784,6 +785,7 @@ void Settings::usage()
     << "  -dev.tv.jitter    <1|0>          Enable TV jitter effect\n"
     << "  -dev.tv.jitter_sense <1-10>      Set TV jitter effect sensitivity\n"
     << "  -dev.tv.jitter_recovery <1-20>   Set recovery time for TV jitter effect\n"
+    << "  -dev.hsrandom     <1|0>          Randomize the hotspot peek values\n"
     << "  -dev.tiadriven    <1|0>          Drive unqused TIA pins randomly on a\n"
     << "                                    read/peek\n"
 #ifdef DEBUGGER_SUPPORT
diff --git a/src/gui/DeveloperDialog.cxx b/src/gui/DeveloperDialog.cxx
index a17b768cc..2df91e469 100644
--- a/src/gui/DeveloperDialog.cxx
+++ b/src/gui/DeveloperDialog.cxx
@@ -56,7 +56,7 @@ DeveloperDialog::DeveloperDialog(OSystem& osystem, DialogContainer& parent,
 
   // Set real dimensions
   setSize(53 * fontWidth + HBORDER * 2,
-          _th + VGAP * 3 + lineHeight + 13 * (lineHeight + VGAP) + buttonHeight + VBORDER * 3,
+          _th + VGAP * 3 + lineHeight + 14 * (lineHeight + VGAP) + buttonHeight + VBORDER * 3,
           max_w, max_h);
 
   // The tab widget
@@ -183,6 +183,12 @@ void DeveloperDialog::addEmulationTab(const GUI::Font& font)
   }
   ypos += lineHeight + VGAP;
 
+  // How to handle undriven TIA pins
+  myRandomHotspotsWidget = new CheckboxWidget(myTab, font, HBORDER + INDENT * 1, ypos + 1,
+                                              "Random hotspot peek values");
+  wid.push_back(myRandomHotspotsWidget);
+  ypos += lineHeight + VGAP;
+
   // How to handle undriven TIA pins
   myUndrivenPinsWidget = new CheckboxWidget(myTab, font, HBORDER + INDENT * 1, ypos + 1,
                                             "Drive unused TIA pins randomly on a read/peek");
@@ -711,6 +717,8 @@ void DeveloperDialog::getWidgetStates(SettingsSet set)
     if(myRandomizeCPUWidget[i]->getState())
       cpurandom += cpuregs[i];
   myRandomizeCPU[set] = cpurandom;
+  // Random hotspot peeks
+  myRandomHotspots[set] = myRandomHotspotsWidget->getState();
   // Undriven TIA pins
   myUndrivenPins[set] = myUndrivenPinsWidget->getState();
 #ifdef DEBUGGER_SUPPORT
@@ -768,6 +776,8 @@ void DeveloperDialog::setWidgetStates(SettingsSet set)
 
   for(int i = 0; i < 5; ++i)
     myRandomizeCPUWidget[i]->setState(BSPF::containsIgnoreCase(cpurandom, cpuregs[i]));
+  // Random hotspot peeks
+  myRandomHotspotsWidget->setState(myRandomHotspots[set]);
   // Undriven TIA pins
   myUndrivenPinsWidget->setState(myUndrivenPins[set]);
 #ifdef DEBUGGER_SUPPORT
@@ -915,6 +925,8 @@ void DeveloperDialog::setDefaults()
       myRandomizeTIA[set] = devSettings;
       myRandomizeRAM[set] = true;
       myRandomizeCPU[set] = devSettings ? "SAXYP" : "AXYP";
+      // Random hotspot peeks
+      myRandomHotspots[set] = devSettings;
       // Undriven TIA pins
       myUndrivenPins[set] = devSettings;
     #ifdef DEBUGGER_SUPPORT
@@ -1091,6 +1103,7 @@ void DeveloperDialog::handleCommand(CommandSender* sender, int cmd, int data, in
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void DeveloperDialog::handleSettings(bool devSettings)
 {
+  myRandomHotspotsWidget->setEnabled(devSettings);
   myUndrivenPinsWidget->setEnabled(devSettings);
 #ifdef DEBUGGER_SUPPORT
   myRWPortBreakWidget->setEnabled(devSettings);
diff --git a/src/gui/DeveloperDialog.hxx b/src/gui/DeveloperDialog.hxx
index def7ba4b9..8b57c6873 100644
--- a/src/gui/DeveloperDialog.hxx
+++ b/src/gui/DeveloperDialog.hxx
@@ -93,8 +93,9 @@ class DeveloperDialog : public Dialog, DevSettingsHandler
     CheckboxWidget*     myRandomizeTIAWidget{nullptr};
     CheckboxWidget*     myRandomizeRAMWidget{nullptr};
     StaticTextWidget*   myRandomizeCPULabel{nullptr};
-    CheckboxWidget*     myUndrivenPinsWidget{nullptr};
     std::array<CheckboxWidget*, 5> myRandomizeCPUWidget{nullptr};
+    CheckboxWidget*     myRandomHotspotsWidget{nullptr};
+    CheckboxWidget*     myUndrivenPinsWidget{nullptr};
 #ifdef DEBUGGER_SUPPORT
     CheckboxWidget*     myRWPortBreakWidget{nullptr};
     CheckboxWidget*     myWRPortBreakWidget{nullptr};