diff --git a/docs/index.html b/docs/index.html
index 66532ffc8..920e43e1b 100644
--- a/docs/index.html
+++ b/docs/index.html
@@ -3621,9 +3621,9 @@
         Note: Mode X (3) is for testing only. It reduces Flash memory access
         clock cycles to always 1.</td>
     </tr><tr>
-      <td><pre>-&lt;plr.|dev.&gt;eepromaccess &lt;1|0&gt;</pre></td>
-      <td>When enabled, each read or write access to the AtariVox/SaveKey EEPROM is
-        signalled by a message.</td>
+      <td><pre>-&lt;plr.|dev.&gt;extaccess &lt;1|0&gt;</pre></td>
+      <td>When enabled, each external access (AtariVox/SaveKey EEPROM, PlusROM, Supercharger...)
+        is signalled by a message.</td>
     </tr><tr>
       <td><pre>-dev.tia.type &lt;standard|koolaidman|cosmicark|</br>  pesco|quickstep|indy500|heman|custom&gt;</pre></td>
       <td>Set emulated TIA type.</td>
@@ -4341,9 +4341,15 @@
             <td>-plr.stats<br/>-dev.stats</td></tr>
           <tr>
             <td>Detected settings info</td>
-            <td>Display detected settings when a ROM is loaded.</td>
+            <td>Display detected settings when a ROM is loaded</td>
             <td>-plr.detectedinfo<br/>-dev.detectedinfo</td>
           </tr>
+          <tr>
+            <td>Display external access message</td>
+            <td>Display a message for any external access
+              (AtariVox/SaveKey EEPROM, PlusROM, Supercharger...)</td>
+            <td>-plr.extaccess<br/>-dev.extaccess</td>
+          </tr>
           <tr>
             <td>Console</td>
             <td>Select the console type, this affects Color/B&W/Pause key
@@ -4391,11 +4397,6 @@
             <td>Thumb ARM emulation throws an exception and enters the debugger on fatal errors</td>
             <td><span style="white-space:nowrap">-dev.thumb.trapfatal</span></td>
           </tr>
-          <tr>
-            <td>Display AtariVox...</td>
-            <td>Display a message when the AtariVox/SaveKey EEPROM is read or written</td>
-            <td>-plr.eepromaccess<br/>-dev.eepromaccess</td>
-          </tr>
         </table>
       </td>
     </tr>
diff --git a/src/emucore/Cart.hxx b/src/emucore/Cart.hxx
index 2922e54f2..05d874a76 100644
--- a/src/emucore/Cart.hxx
+++ b/src/emucore/Cart.hxx
@@ -144,7 +144,7 @@ class Cartridge : public Device
     /**
       Set the callback for displaying messages
     */
-    void setMessageCallback(const messageCallback& callback)
+    virtual void setMessageCallback(const messageCallback& callback)
     {
       myMsgCallback = callback;
     }
diff --git a/src/emucore/CartARM.cxx b/src/emucore/CartARM.cxx
index 4459bdc29..791ba858a 100644
--- a/src/emucore/CartARM.cxx
+++ b/src/emucore/CartARM.cxx
@@ -25,6 +25,13 @@ CartridgeARM::CartridgeARM(const string& md5, const Settings& settings)
 {
 }
 
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void CartridgeARM::reset()
+{
+  if(myPlusROM->isValid())
+    myPlusROM->reset();
+}
+
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void CartridgeARM::setInitialState()
 {
@@ -96,6 +103,9 @@ bool CartridgeARM::save(Serializer& out) const
     out.putInt(myPrevStats.instructions);
     out.putInt(myCycles);
     out.putInt(myStats.instructions);
+
+    if(myPlusROM->isValid() && !myPlusROM->save(out))
+      return false;
   }
   catch(...)
   {
@@ -116,6 +126,9 @@ bool CartridgeARM::load(Serializer& in)
     myPrevStats.instructions = in.getInt();
     myCycles = in.getInt();
     myStats.instructions = in.getInt();
+
+    if(myPlusROM->isValid() && !myPlusROM->load(in))
+      return false;
   }
   catch(...)
   {
diff --git a/src/emucore/CartARM.hxx b/src/emucore/CartARM.hxx
index d43b4e17d..2ebdf43dd 100644
--- a/src/emucore/CartARM.hxx
+++ b/src/emucore/CartARM.hxx
@@ -19,6 +19,7 @@
 #define CARTRIDGE_ARM_HXX
 
 #include "Thumbulator.hxx"
+#include "PlusROM.hxx"
 #include "Cart.hxx"
 
 /**
@@ -34,6 +35,11 @@ class CartridgeARM : public Cartridge
     CartridgeARM(const string& md5, const Settings& settings);
     ~CartridgeARM() override = default;
 
+    /**
+      Reset device to its power-on state
+    */
+    void reset() override;
+
   protected:
     /**
       Notification method invoked by the system when the console type
@@ -85,10 +91,23 @@ class CartridgeARM : public Cartridge
     void setMamMode(Thumbulator::MamModeType mamMode) { myThumbEmulator->setMamMode(mamMode); }
     Thumbulator::MamModeType mamMode() const { return myThumbEmulator->mamMode(); }
 
+    /**
+      Set the callback for displaying messages
+    */
+    void setMessageCallback(const messageCallback& callback) override
+    {
+      Cartridge::setMessageCallback(callback);
+      if(myPlusROM->isValid())
+        myPlusROM->setMessageCallback(myMsgCallback);
+    }
+
   protected:
     // Pointer to the Thumb ARM emulator object
     unique_ptr<Thumbulator> myThumbEmulator;
 
+    // Handle PlusROM functionality, if available
+    unique_ptr<PlusROM> myPlusROM;
+
     // ARM code increases 6507 cycles
     bool myIncCycles{false};
 
diff --git a/src/emucore/CartCDF.cxx b/src/emucore/CartCDF.cxx
index 1aba0ab12..fa46611be 100644
--- a/src/emucore/CartCDF.cxx
+++ b/src/emucore/CartCDF.cxx
@@ -113,6 +113,11 @@ CartridgeCDF::CartridgeCDF(const ByteBuffer& image, size_t size,
     this);
 
   setInitialState();
+
+  myPlusROM = make_unique<PlusROM>(mySettings);
+
+  // Determine whether we have a PlusROM cart
+  myPlusROM->initialize(myImage, mySize);
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@@ -130,6 +135,8 @@ void CartridgeCDF::reset()
 
   // Upon reset we switch to the startup bank
   bank(startBank());
+
+  CartridgeARM::reset();
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@@ -213,6 +220,14 @@ inline void CartridgeCDF::callFunction(uInt8 value)
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 uInt8 CartridgeCDF::peek(uInt16 address)
 {
+  // Is this a PlusROM?
+  if(myPlusROM->isValid())
+  {
+    uInt8 value = 0;
+    if(myPlusROM->peekHotspot(address, value))
+      return value;
+  }
+
   address &= 0x0FFF;
   uInt8 peekvalue = myProgramImage[myBankOffset + address];
 
@@ -356,6 +371,10 @@ bool CartridgeCDF::poke(uInt16 address, uInt8 value)
 {
   uInt32 pointer;
 
+  // Is this a PlusROM?
+  if(myPlusROM->isValid() && myPlusROM->pokeHotspot(address, value))
+    return true;
+
   address &= 0x0FFF;
   switch(address)
   {
diff --git a/src/emucore/CartCDF.hxx b/src/emucore/CartCDF.hxx
index 621873e9f..fea1c0165 100644
--- a/src/emucore/CartCDF.hxx
+++ b/src/emucore/CartCDF.hxx
@@ -253,6 +253,14 @@ class CartridgeCDF : public CartridgeARM
     uInt32 getSample();
     void setupVersion();
 
+    /**
+      Answer whether this is a PlusROM cart.  Note that until the
+      initialize method has been called, this will always return false.
+
+      @return  Whether this is actually a PlusROM cart
+    */
+    bool isPlusROM() const override { return myPlusROM->isValid(); }
+
   private:
     // The ROM image of the cartridge
     ByteBuffer myImage{nullptr};
diff --git a/src/emucore/CartDPCPlus.cxx b/src/emucore/CartDPCPlus.cxx
index 7fac7dda3..377928ae6 100644
--- a/src/emucore/CartDPCPlus.cxx
+++ b/src/emucore/CartDPCPlus.cxx
@@ -79,6 +79,11 @@ CartridgeDPCPlus::CartridgeDPCPlus(const ByteBuffer& image, size_t size,
     myFractionalLowMask = 0x0F0000;
 
   setInitialState();
+
+  myPlusROM = make_unique<PlusROM>(mySettings);
+
+  // Determine whether we have a PlusROM cart
+  myPlusROM->initialize(myImage, mySize);
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@@ -91,6 +96,8 @@ void CartridgeDPCPlus::reset()
 
   // Upon reset we switch to the startup bank
   bank(startBank());
+
+  CartridgeARM::reset();
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@@ -218,6 +225,14 @@ inline void CartridgeDPCPlus::callFunction(uInt8 value)
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 uInt8 CartridgeDPCPlus::peek(uInt16 address)
 {
+  // Is this a PlusROM?
+  if(myPlusROM->isValid())
+  {
+    uInt8 value = 0;
+    if(myPlusROM->peekHotspot(address, value))
+      return value;
+  }
+
   address &= 0x0FFF;
 
   uInt8 peekvalue = myProgramImage[myBankOffset + address];
@@ -405,6 +420,10 @@ uInt8 CartridgeDPCPlus::peek(uInt16 address)
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 bool CartridgeDPCPlus::poke(uInt16 address, uInt8 value)
 {
+  // Is this a PlusROM?
+  if(myPlusROM->isValid() && myPlusROM->pokeHotspot(address, value))
+    return true;
+
   address &= 0x0FFF;
 
   if((address >= 0x0028) && (address < 0x0080))
diff --git a/src/emucore/CartDPCPlus.hxx b/src/emucore/CartDPCPlus.hxx
index a52ba8338..37fad81fb 100644
--- a/src/emucore/CartDPCPlus.hxx
+++ b/src/emucore/CartDPCPlus.hxx
@@ -149,6 +149,13 @@ class CartridgeDPCPlus : public CartridgeARM
     */
     uInt8 internalRamGetValue(uInt16 addr) const override;
 
+    /**
+      Answer whether this is a PlusROM cart.  Note that until the
+      initialize method has been called, this will always return false.
+
+      @return  Whether this is actually a PlusROM cart
+    */
+    bool isPlusROM() const override { return myPlusROM->isValid(); }
 
   #ifdef DEBUGGER_SUPPORT
     /**
diff --git a/src/emucore/CartEnhanced.hxx b/src/emucore/CartEnhanced.hxx
index ea8438ee5..2ee3b5a75 100644
--- a/src/emucore/CartEnhanced.hxx
+++ b/src/emucore/CartEnhanced.hxx
@@ -157,6 +157,14 @@ class CartridgeEnhanced : public Cartridge
     */
     bool poke(uInt16 address, uInt8 value) override;
 
+    /**
+      Get the hotspot in ROM address space.
+
+      @return  The first hotspot address (usually in ROM) space or 0
+    */
+    virtual uInt16 hotspot() const { return 0; }
+    // TODO: handle cases where there the hotspots cover multiple pages
+
     /**
       Answer whether this is a PlusROM cart.  Note that until the
       initialize method has been called, this will always return false.
@@ -166,12 +174,14 @@ class CartridgeEnhanced : public Cartridge
     bool isPlusROM() const override { return myPlusROM->isValid(); }
 
     /**
-      Get the hotspot in ROM address space.
-
-      @return  The first hotspot address (usually in ROM) space or 0
+      Set the callback for displaying messages
     */
-    virtual uInt16 hotspot() const { return 0; }
-    // TODO: handle cases where there the hotspots cover multiple pages
+    void setMessageCallback(const messageCallback& callback) override
+    {
+      Cartridge::setMessageCallback(callback);
+      if(myPlusROM->isValid())
+        myPlusROM->setMessageCallback(myMsgCallback);
+    }
 
   protected:
     // The '2 ^ N = bank segment size' exponent
diff --git a/src/emucore/Console.cxx b/src/emucore/Console.cxx
index 7787e6512..791e982dd 100644
--- a/src/emucore/Console.cxx
+++ b/src/emucore/Console.cxx
@@ -957,7 +957,7 @@ unique_ptr<Controller> Console::getControllerPort(const Controller::Type type,
       nvramfile /= "atarivox_eeprom.dat";
       Controller::onMessageCallback callback = [&os = myOSystem](const string& msg) {
         bool devSettings = os.settings().getBool("dev.settings");
-        if(os.settings().getBool(devSettings ? "dev.eepromaccess" : "plr.eepromaccess"))
+        if(os.settings().getBool(devSettings ? "dev.extaccess" : "plr.extaccess"))
           os.frameBuffer().showTextMessage(msg);
       };
       controller = make_unique<AtariVox>(port, myEvent, *mySystem,
@@ -970,7 +970,7 @@ unique_ptr<Controller> Console::getControllerPort(const Controller::Type type,
       nvramfile /= "savekey_eeprom.dat";
       Controller::onMessageCallback callback = [&os = myOSystem](const string& msg) {
         bool devSettings = os.settings().getBool("dev.settings");
-        if(os.settings().getBool(devSettings ? "dev.eepromaccess" : "plr.eepromaccess"))
+        if(os.settings().getBool(devSettings ? "dev.extaccess" : "plr.extaccess"))
           os.frameBuffer().showTextMessage(msg);
       };
       controller = make_unique<SaveKey>(port, myEvent, *mySystem, nvramfile, callback);
diff --git a/src/emucore/OSystem.cxx b/src/emucore/OSystem.cxx
index 8a2f3601f..a1be2412d 100644
--- a/src/emucore/OSystem.cxx
+++ b/src/emucore/OSystem.cxx
@@ -636,7 +636,7 @@ unique_ptr<Console> OSystem::openConsole(const FilesystemNode& romfile, string&
     {
       bool devSettings = os.settings().getBool("dev.settings");
 
-      if(os.settings().getBool(devSettings ? "dev.eepromaccess" : "plr.eepromaccess"))
+      if(os.settings().getBool(devSettings ? "dev.extaccess" : "plr.extaccess"))
         os.frameBuffer().showTextMessage(msg);
     };
 
diff --git a/src/emucore/PlusROM.cxx b/src/emucore/PlusROM.cxx
index 78c13f945..3476dfd4c 100644
--- a/src/emucore/PlusROM.cxx
+++ b/src/emucore/PlusROM.cxx
@@ -382,7 +382,22 @@ void PlusROM::send()
     // The lambda will retain a copy of the shared_ptr that is alive as long as the
     // thread is running. Thus, the request can only be destructed once the thread has
     // finished, and we can safely evict it from the deque at any time.
-    std::thread thread([=]() { request->execute(); });
+    std::thread thread([=]() {
+      request->execute();
+      switch(request->getState())
+      {
+        case PlusROMRequest::State::failed:
+          myMsgCallback("PlusROM data sending failed!");
+          break;
+
+        case PlusROMRequest::State::done:
+          myMsgCallback("PlusROM data sent successfully");
+          break;
+
+        default:
+          break;
+      }
+    });
 
     thread.detach();
   }
@@ -398,14 +413,15 @@ void PlusROM::receive()
   while (iter != myPendingRequests.end()) {
     switch ((*iter)->getState()) {
       case PlusROMRequest::State::failed:
+        myMsgCallback("PlusROM data receiving failed!");
         // Request has failed? -> remove it and start over
         myPendingRequests.erase(iter);
         iter = myPendingRequests.begin();
-
         continue;
 
       case PlusROMRequest::State::done:
       {
+        myMsgCallback("PlusROM data received successfully");
         // Request has finished sucessfully? -> consume the response, remove it
         // and start over
         auto [responseSize, response] = (*iter)->getResponse();
@@ -415,7 +431,6 @@ void PlusROM::receive()
 
         myPendingRequests.erase(iter);
         iter = myPendingRequests.begin();
-
         continue;
       }
 
diff --git a/src/emucore/PlusROM.hxx b/src/emucore/PlusROM.hxx
index 19470b2b2..790307372 100644
--- a/src/emucore/PlusROM.hxx
+++ b/src/emucore/PlusROM.hxx
@@ -24,6 +24,7 @@ class Settings;
 
 #include "bspf.hxx"
 #include "Serializable.hxx"
+#include "Cart.hxx"
 
 /**
   Class used to emulate the 'PlusROM' meta-scheme, documented at
@@ -120,6 +121,14 @@ class PlusROM : public Serializable
     */
     void reset();
 
+    /**
+      Set the callback for displaying messages
+    */
+    void setMessageCallback(const Cartridge::messageCallback& callback)
+    {
+      myMsgCallback = callback;
+    }
+
   private:
     bool isValidHost(const string& host) const;
     bool isValidPath(const string& path) const;
@@ -145,6 +154,9 @@ class PlusROM : public Serializable
 
     std::deque<shared_ptr<PlusROMRequest>> myPendingRequests;
 
+    // Callback to output messages
+    Cartridge::messageCallback myMsgCallback{nullptr};
+
   private:
     // Following constructors and assignment operators not supported
     PlusROM(const PlusROM&) = delete;
diff --git a/src/emucore/QuadTari.cxx b/src/emucore/QuadTari.cxx
index ce828aa05..63779cb96 100644
--- a/src/emucore/QuadTari.cxx
+++ b/src/emucore/QuadTari.cxx
@@ -71,7 +71,7 @@ unique_ptr<Controller> QuadTari::addController(const Controller::Type type, bool
   FilesystemNode nvramfile = myOSystem.nvramDir();
   Controller::onMessageCallback callback = [&os = myOSystem](const string& msg) {
     bool devSettings = os.settings().getBool("dev.settings");
-    if(os.settings().getBool(devSettings ? "dev.eepromaccess" : "plr.eepromaccess"))
+    if(os.settings().getBool(devSettings ? "dev.extaccess" : "plr.extaccess"))
       os.frameBuffer().showTextMessage(msg);
   };
 
diff --git a/src/emucore/Settings.cxx b/src/emucore/Settings.cxx
index 355f01e5a..c091f5756 100644
--- a/src/emucore/Settings.cxx
+++ b/src/emucore/Settings.cxx
@@ -220,7 +220,7 @@ Settings::Settings()
   setPermanent("plr.tm.interval", "30f"); // = 0.5 seconds
   setPermanent("plr.tm.horizon", "10m"); // = ~10 minutes
   setPermanent("plr.detectedinfo", "false");
-  setPermanent("plr.eepromaccess", "false");
+  setPermanent("plr.extaccess", "false");
 
   // Developer settings
   setPermanent("dev.settings", "false");
@@ -250,7 +250,7 @@ Settings::Settings()
   setPermanent("dev.tm.interval", "1f"); // = 1 frame
   setPermanent("dev.tm.horizon", "30s"); // = ~30 seconds
   setPermanent("dev.detectedinfo", "true");
-  setPermanent("dev.eepromaccess", "true");
+  setPermanent("dev.extaccess", "true");
   // Thumb ARM emulation options
   setPermanent("dev.thumb.trapfatal", "true");
 #ifdef DEBUGGER_SUPPORT
@@ -684,8 +684,7 @@ void Settings::usage() const
     << "  -plr.colorloss    <1|0>          Enable PAL color-loss effect\n"
     << "  -plr.tv.jitter    <1|0>          Enable TV jitter effect\n"
     << "  -plr.tv.jitter_recovery <1-20>   Set recovery time for TV jitter effect\n"
-    << "  -plr.eepromaccess <1|0>          Enable messages for AtariVox/SaveKey access\n"
-    << "                                    messages\n"
+    << "  -plr.extaccess    <1|0>          Enable messages for external access\n"
     << endl
     << " The same parameters but for developer settings mode\n"
     << "  -dev.stats        <1|0>          Overlay console info during emulation\n"
@@ -716,8 +715,7 @@ void Settings::usage() const
     << "  -dev.thumb.chiptype    <0|1>     Selects the ARM chip type\n"
     << "  -dev.thumb.mammode     <0-3>     Selects the LPC's MAM mode\n"
 #endif
-    << "  -dev.eepromaccess      <1|0>     Enable messages for AtariVox/SaveKey access\n"
-    << "                                    messages\n"
+    << "  -dev.extaccess         <1|0>     Enable messages for external access\n"
     << "  -dev.tia.type <standard|custom|  Selects a TIA type\n"
     << "                 koolaidman|\n"
     << "                 cosmicark|pesco|\n"
diff --git a/src/gui/DeveloperDialog.cxx b/src/gui/DeveloperDialog.cxx
index 4e6a037af..6e96a39cb 100644
--- a/src/gui/DeveloperDialog.cxx
+++ b/src/gui/DeveloperDialog.cxx
@@ -123,9 +123,9 @@ void DeveloperDialog::addEmulationTab(const GUI::Font& font)
 
   // AtariVox/SaveKey/PlusROM access
   myExternAccessWidget = new CheckboxWidget(myTab, font, HBORDER + INDENT * 1, ypos + 1,
-                                            "Display AtariVox/SaveKey and PlusROM access");
-  myExternAccessWidget->setToolTip("Display message when AtariVox/SaveKey EEPROM\n"
-                                   "is read or written or PlusROM is accessed.");
+                                            "Display external access message");
+  myExternAccessWidget->setToolTip("Display a message for any external access\n"
+                                   "AtariVox/SaveKey EEPROM, PlusROM, Supercharger...).");
   wid.push_back(myExternAccessWidget);
   ypos += lineHeight + VGAP;
 
@@ -687,7 +687,7 @@ void DeveloperDialog::loadSettings(SettingsSet set)
   // Thumb ARM emulation exception
   myThumbException[set] = devSettings ? instance().settings().getBool("dev.thumb.trapfatal") : false;
   // AtariVox/SaveKey/PlusROM access
-  myExternAccess[set] = instance().settings().getBool(prefix + "eepromaccess");
+  myExternAccess[set] = instance().settings().getBool(prefix + "extaccess");
 
   // TIA tab
   myTIAType[set] = devSettings ? instance().settings().getString("dev.tia.type") : "standard";
@@ -749,7 +749,7 @@ void DeveloperDialog::saveSettings(SettingsSet set)
   }
 
   // AtariVox/SaveKey/PlusROM access
-  instance().settings().setValue(prefix + "eepromaccess", myExternAccess[set]);
+  instance().settings().setValue(prefix + "extaccess", myExternAccess[set]);
 
   // TIA tab
   if (devSettings)