added limited GameLine Master Module bankswitching support

Changes.txt

@@ -34,6 +34,8 @@
 
   * Acclerated emulation up to ~15% (ARM).
 
+  * Added limited GameLine Master Module bankswitching support.
+
   * Added BUS bankswitching support for some older demos.
 
   * Fixed broken 7800 pause key support.

docs/index.html

@@ -4947,6 +4947,7 @@ Ms Pac-Man (Stella extended codes):
         <tr><td>FA2 </td><td>CBS RAM Plus 24/28K </td><td>.FA2 </td></tr>
         <tr><td>FC </td><td>Amiga Power Play Aracde 16/32K </td><td>.FC </td></tr>
         <tr><td>FE </td><td>8K Activision (aka SCABS)</td><td>.FE </td></tr>
+		<tr><td>GL </td><td>GameLine Master Module</td><td>.GL </td></tr>
         <tr><td>MDM </td><td>Menu Driven Megacart </td><td>.MDM </td></tr>
         <tr><td>MVC </td><td>Movie Cart</td><td>.MVC </td></tr>
         <tr><td>SB </td><td>128-256K SUPERbanking </td><td>.SB </td></tr>

src/debugger/gui/Cart4KWidget.cxx

@@ -25,16 +25,6 @@ Cartridge4KWidget::Cartridge4KWidget(
   : CartridgeEnhancedWidget(boss, lfont, nfont, x, y, w, h, cart)
 {
   initialize();
-
-  //// Eventually, we should query this from the debugger/disassembler
-  //uInt16 start = (cart.myImage[0xFFD] << 8) | cart.myImage[0xFFC];
-  //start -= start % 0x1000;
-
-  //ostringstream info;
-  //info << "Standard 4K cartridge, non-bankswitched\n"
-  //     << "Accessible @ $" << Common::Base::HEX4 << start << " - "
-  //     << "$" << (start + 0xFFF);
-  //addBaseInformation(4096, "Atari", info.str());
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

src/debugger/gui/CartEnhancedWidget.cxx

@@ -181,11 +181,20 @@ void CartridgeEnhancedWidget::bankList(uInt16 bankCount, int seg, VariantList& i
 {
   width = 0;
 
+  const bool hasRamBanks = myCart.myRamBankCount > 0;
+
   for(int bank = 0; bank < bankCount; ++bank)
   {
     ostringstream buf;
+    const bool isRamBank = (bank >= myCart.romBankCount());
+    const int bankNum = (bank - (isRamBank ? myCart.romBankCount() : 0));
+
+    buf << std::setw(bankNum < 10 ? 2 : 1) << "#" << std::dec << bankNum;
+    if(isRamBank) // was RAM mapped here?
+      buf << " RAM";
+    else if (hasRamBanks)
+      buf << " ROM";
 
-    buf << std::setw(bank < 10 ? 2 : 1) << "#" << std::dec << bank;
     if(myCart.hotspot() != 0 && myHotspotDelta > 0)
       buf << " " << hotspotStr(bank, seg);
     VarList::push_back(items, buf.str());
@@ -196,7 +205,7 @@ void CartridgeEnhancedWidget::bankList(uInt16 bankCount, int seg, VariantList& i
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void CartridgeEnhancedWidget::bankSelect(int& ypos)
 {
-  if(myCart.romBankCount() > 1)
+  if(myCart.romBankCount() + myCart.ramBankCount() > 1)
   {
     constexpr int xpos = 2;
 
@@ -208,7 +217,7 @@ void CartridgeEnhancedWidget::bankSelect(int& ypos)
       VariantList items;
       int pw = 0;
 
-      bankList(myCart.romBankCount(), seg, items, pw);
+      bankList(myCart.romBankCount() + myCart.ramBankCount(), seg, items, pw);
 
       // create widgets
       ostringstream buf;
@@ -249,7 +258,6 @@ string CartridgeEnhancedWidget::bankState()
         const int bank = myCart.getSegmentBank(seg);
         const bool isRamBank = (bank >= myCart.romBankCount());
 
-
         if(seg > 0)
           buf << " / ";
 

src/debugger/gui/CartGLWidget.cxx

@@ -0,0 +1,50 @@
+//============================================================================
+//
+//   SSSS    tt          lll  lll
+//  SS  SS   tt           ll   ll
+//  SS     tttttt  eeee   ll   ll   aaaa
+//   SSSS    tt   ee  ee  ll   ll      aa
+//      SS   tt   eeeeee  ll   ll   aaaaa  --  "An Atari 2600 VCS Emulator"
+//  SS  SS   tt   ee      ll   ll  aa  aa
+//   SSSS     ttt  eeeee llll llll  aaaaa
+//
+// Copyright (c) 1995-2023 by Bradford W. Mott, Stephen Anthony
+// and the Stella Team
+//
+// See the file "License.txt" for information on usage and redistribution of
+// this file, and for a DISCLAIMER OF ALL WARRANTIES.
+//============================================================================
+
+#include "CartGL.hxx"
+#include "CartGLWidget.hxx"
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+CartridgeGLWidget::CartridgeGLWidget(
+    GuiObject* boss, const GUI::Font& lfont, const GUI::Font& nfont,
+    int x, int y, int w, int h, CartridgeGL& cart)
+  : CartridgeEnhancedWidget(boss, lfont, nfont, x, y, w, h, cart)
+{
+  initialize();
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+string CartridgeGLWidget::description()
+{
+  ostringstream info;
+
+  info << "GameLine Master Module cartridge, 4K ROM, 10/12K RAM\n"
+    << "mapped into four 1K segments\n"
+    << "THIS SCHEME IS NOT FULLY IMPLEMENTED OR TESTED";
+
+  return info.str();
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+string CartridgeGLWidget::internalRamDescription()
+{
+  ostringstream desc;
+
+  desc << "Accessible 1K" << " at a time";
+
+  return desc.str();
+}

src/debugger/gui/CartGLWidget.hxx

@@ -0,0 +1,50 @@
+//============================================================================
+//
+//   SSSS    tt          lll  lll
+//  SS  SS   tt           ll   ll
+//  SS     tttttt  eeee   ll   ll   aaaa
+//   SSSS    tt   ee  ee  ll   ll      aa
+//      SS   tt   eeeeee  ll   ll   aaaaa  --  "An Atari 2600 VCS Emulator"
+//  SS  SS   tt   ee      ll   ll  aa  aa
+//   SSSS     ttt  eeeee llll llll  aaaaa
+//
+// Copyright (c) 1995-2023 by Bradford W. Mott, Stephen Anthony
+// and the Stella Team
+//
+// See the file "License.txt" for information on usage and redistribution of
+// this file, and for a DISCLAIMER OF ALL WARRANTIES.
+//============================================================================
+
+#ifndef CARTRIDGEGL_WIDGET_HXX
+#define CARTRIDGEGL_WIDGET_HXX
+
+class CartridgeGL;
+
+#include "CartEnhanced.hxx"
+
+class CartridgeGLWidget : public CartridgeEnhancedWidget
+{
+  public:
+    CartridgeGLWidget(GuiObject* boss, const GUI::Font& lfont,
+                      const GUI::Font& nfont,
+                      int x, int y, int w, int h,
+                      CartridgeGL& cart);
+    ~CartridgeGLWidget() override = default;
+
+  private:
+    string manufacturer() override { return "Control Video Corporation (CVC)"; }
+
+    string description() override;
+
+    string internalRamDescription() override;
+
+  private:
+    // Following constructors and assignment operators not supported
+    CartridgeGLWidget() = delete;
+    CartridgeGLWidget(const CartridgeGLWidget&) = delete;
+    CartridgeGLWidget(CartridgeGLWidget&&) = delete;
+    CartridgeGLWidget& operator=(const CartridgeGLWidget&) = delete;
+    CartridgeGLWidget& operator=(CartridgeGLWidget&&) = delete;
+};
+
+#endif

src/debugger/gui/module.mk

@@ -46,6 +46,7 @@ MODULE_OBJS := \
         src/debugger/gui/CartFAWidget.o \
         src/debugger/gui/CartFCWidget.o \
         src/debugger/gui/CartFEWidget.o \
+	src/debugger/gui/CartGLWidget.o \
         src/debugger/gui/CartMDMWidget.o \
         src/debugger/gui/CartRamWidget.o \
         src/debugger/gui/CartSBWidget.o \

src/emucore/Bankswitch.cxx

@@ -119,6 +119,7 @@ Bankswitch::BSList = {{
   { "FA2"     , "FA2 (CBS RAM Plus 24-32K)"   },
   { "FC"      , "FC (32K Amiga)"              },
   { "FE"      , "FE (8K Activision)"          },
+  { "GL"      , "GL (GameLine Master Module)" },
   { "MDM"     , "MDM (Menu Driven Megacart)"  },
   { "MVC"     , "MVC (Movie Cart)"            },
   { "SB"      , "SB (128-256K SUPERbank)"     },
@@ -129,7 +130,7 @@ Bankswitch::BSList = {{
   { "WDSW"    , "WDSW (Pink Panther, bad)"    },
   { "X07"     , "X07 (64K AtariAge)"          },
 #if defined(CUSTOM_ARM)
-  { "CUSTOM"  ,   "CUSTOM (ARM)"                  }
+  { "CUSTOM"  ,   "CUSTOM (ARM)"              }
 #endif
 }};
 
@@ -181,6 +182,7 @@ Bankswitch::Sizes = {{
   {   24_KB,  32_KB }, // _FA2
   {   32_KB,  32_KB }, // _FC
   {    8_KB,   8_KB }, // _FE
+  {    4_KB,   4_KB }, // _GL
   {    8_KB, Bankswitch::any_KB }, // _MDM
   { 1024_KB, Bankswitch::any_KB }, // _MVC
   {  128_KB, 256_KB }, // _SB
@@ -270,6 +272,7 @@ Bankswitch::ExtensionMap Bankswitch::ourExtensions = {
   { "FA2"   , Bankswitch::Type::_FA2    },
   { "FC"    , Bankswitch::Type::_FC     },
   { "FE"    , Bankswitch::Type::_FE     },
+  { "GL"    , Bankswitch::Type::_GL     },
   { "MDM"   , Bankswitch::Type::_MDM    },
   { "MVC"   , Bankswitch::Type::_MVC    },
   { "SB"    , Bankswitch::Type::_SB     },
@@ -329,6 +332,7 @@ Bankswitch::NameToTypeMap Bankswitch::ourNameToTypes = {
   { "FA2"     , Bankswitch::Type::_FA2    },
   { "FC"      , Bankswitch::Type::_FC     },
   { "FE"      , Bankswitch::Type::_FE     },
+  { "GL"      , Bankswitch::Type::_GL     },
   { "MDM"     , Bankswitch::Type::_MDM    },
   { "MVC"     , Bankswitch::Type::_MVC    },
   { "SB"      , Bankswitch::Type::_SB     },

src/emucore/Bankswitch.hxx

@@ -43,8 +43,8 @@ class Bankswitch
       _4K,    _4KSC,   _AR,   _BF,   _BFSC, _BUS,  _CDF,   _CM,
       _CTY,   _CV,     _DF,   _DFSC, _DPC,  _DPCP, _E0,    _E7,
       _EF,    _EFSC,   _F0,   _F4,   _F4SC, _F6,   _F6SC,  _F8,
-      _F8SC,  _FA,     _FA2,  _FC,   _FE,   _MDM,  _MVC,   _SB,
+      _F8SC,  _FA,     _FA2,  _FC,   _FE,   _GL,   _MDM,   _MVC,
-      _TVBOY, _UA,     _UASW, _WD,   _WDSW, _X07,
+      _SB,    _TVBOY,  _UA,   _UASW, _WD,   _WDSW, _X07,
     #ifdef CUSTOM_ARM
       _CUSTOM,
     #endif

src/emucore/Cart.hxx

@@ -434,6 +434,9 @@ class Cartridge : public Device
     // Callback to output messages
     messageCallback myMsgCallback{nullptr};
 
+    // Semi-random values to use when a read from write port occurs
+    std::array<uInt8, 256> myRWPRandomValues;
+
   private:
     // The startup bank to use (where to look for the reset vector address)
     uInt16 myStartBank{0};
@@ -442,9 +445,6 @@ class Cartridge : public Device
     // by the debugger, when disassembling/dumping ROM.
     bool myHotspotsLocked{false};
 
-    // Semi-random values to use when a read from write port occurs
-    std::array<uInt8, 256> myRWPRandomValues;
-
     // Contains various info about this cartridge
     // This needs to be stored separately from child classes, since
     // sometimes the information in both do not match

src/emucore/CartCreator.cxx

@@ -54,6 +54,7 @@
 #include "CartFA2.hxx"
 #include "CartFC.hxx"
 #include "CartFE.hxx"
+#include "CartGL.hxx"
 #include "CartMDM.hxx"
 #include "CartMVC.hxx"
 #include "CartSB.hxx"
@@ -305,6 +306,8 @@ CartCreator::createFromImage(const ByteBuffer& image, size_t size,
       return make_unique<CartridgeFC>(image, size, md5, settings);
     case Bankswitch::Type::_FE:
       return make_unique<CartridgeFE>(image, size, md5, settings);
+    case Bankswitch::Type::_GL:
+      return make_unique<CartridgeGL>(image, size, md5, settings);
     case Bankswitch::Type::_MDM:
       return make_unique<CartridgeMDM>(image, size, md5, settings);
     case Bankswitch::Type::_UA:

src/emucore/CartDetector.cxx

@@ -27,9 +27,12 @@ Bankswitch::Type CartDetector::autodetectType(const ByteBuffer& image, size_t si
   // Guess type based on size
   Bankswitch::Type type = Bankswitch::Type::_AUTO;
 
-  if((size % 8448) == 0 || size == 6144)
+  if((size % 8448) == 0 || size == 6_KB)
   {
-    type = Bankswitch::Type::_AR;
+    if(size == 6_KB && isProbablyGL(image, size))
+      type = Bankswitch::Type::_GL;
+    else
+      type = Bankswitch::Type::_AR;
   }
   else if(size < 2_KB)  // Sub2K images
   {
@@ -48,6 +51,8 @@ Bankswitch::Type CartDetector::autodetectType(const ByteBuffer& image, size_t si
       type = Bankswitch::Type::_4KSC;
     else if (isProbablyFC(image, size))
       type = Bankswitch::Type::_FC;
+    else if (isProbablyGL(image, size))
+      type = Bankswitch::Type::_GL;
     else
       type = Bankswitch::Type::_4K;
   }
@@ -706,6 +711,14 @@ bool CartDetector::isProbablyFE(const ByteBuffer& image, size_t size)
   return false;
 }
 
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+bool CartDetector::isProbablyGL(const ByteBuffer& image, size_t size)
+{
+  static constexpr uInt8 signature[] = { 0xad, 0xb8, 0x0c };  // LDA $0CB8
+
+  return searchForBytes(image, size, signature, 3);
+}
+
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 bool CartDetector::isProbablyMDM(const ByteBuffer& image, size_t size)
 {

src/emucore/CartDetector.hxx

@@ -201,6 +201,11 @@ class CartDetector
     */
     static bool isProbablyFE(const ByteBuffer& image, size_t size);
 
+    /**
+      Returns true if the image is probably a GameLine cartridge
+    */
+    static bool isProbablyGL(const ByteBuffer& image, size_t size);
+
     /**
       Returns true if the image is probably a MDM bankswitching cartridge
     */

src/emucore/CartEnhanced.cxx

@@ -65,8 +65,11 @@ CartridgeEnhanced::CartridgeEnhanced(const ByteBuffer& image, size_t size,
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void CartridgeEnhanced::install(System& system)
 {
+  if(!myRamBankShift)
+    myRamBankShift = myBankShift - 1;
+
   // limit banked RAM size to the size of one RAM bank
-  const uInt16 ramSize = myRamBankCount > 0 ? 1 << (myBankShift - 1) :
+  const uInt16 ramSize = myRamBankCount > 0 ? 1 << myRamBankShift :
     static_cast<uInt16>(myRamSize);
 
   // calculate bank switching and RAM sizes and masks
@@ -200,7 +203,8 @@ bool CartridgeEnhanced::poke(uInt16 address, uInt8 value)
 
     if(isRamBank(address))
     {
-      if(static_cast<bool>(address & (myBankSize >> 1)) == myRamWpHigh)
+      if(static_cast<bool>(address & (myBankSize >> 1)) == myRamWpHigh
+        || myBankShift == myRamBankShift)
       {
         address &= myRamMask;
         // The RAM banks follow the ROM banks and are half the size of a ROM bank
@@ -271,7 +275,7 @@ bool CartridgeEnhanced::bank(uInt16 bank, uInt16 segment)
     const uInt16 ramBank = (bank - romBankCount()) % myRamBankCount;
     // The RAM banks follow the ROM banks and are half the size of a ROM bank
     const uInt32 bankOffset = static_cast<uInt32>(mySize) +
-      (ramBank << (myBankShift - 1));
+      (ramBank << myRamBankShift);
 
     // Remember what bank is in this segment
     myCurrentSegOffset[segment] = static_cast<uInt32>(mySize) +
@@ -280,7 +284,8 @@ bool CartridgeEnhanced::bank(uInt16 bank, uInt16 segment)
     // Set the page accessing method for the RAM writing pages
     // Note: Writes are mapped to poke() (NOT using directPokeBase) to check for read from write port (RWP)
     uInt16 fromAddr = (ROM_OFFSET + segmentOffset + myWriteOffset) & ~System::PAGE_MASK;
-    uInt16 toAddr   = (ROM_OFFSET + segmentOffset + myWriteOffset + (myBankSize >> 1)) & ~System::PAGE_MASK;
+    uInt16 toAddr   = (ROM_OFFSET + segmentOffset + myWriteOffset
+      + (myBankSize >> (myBankShift - myRamBankShift))) & ~System::PAGE_MASK;
     System::PageAccess access(this, System::PageAccessType::WRITE);
 
     for(uInt16 addr = fromAddr; addr < toAddr; addr += System::PAGE_SIZE)
@@ -295,7 +300,8 @@ bool CartridgeEnhanced::bank(uInt16 bank, uInt16 segment)
 
     // Set the page accessing method for the RAM reading pages
     fromAddr = (ROM_OFFSET + segmentOffset + myReadOffset) & ~System::PAGE_MASK;
-    toAddr   = (ROM_OFFSET + segmentOffset + myReadOffset + (myBankSize >> 1)) & ~System::PAGE_MASK;
+    toAddr   = (ROM_OFFSET + segmentOffset + myReadOffset 
+      + (myBankSize >> (myBankShift - myRamBankShift))) & ~System::PAGE_MASK;
     access.type = System::PageAccessType::READ;
 
     for(uInt16 addr = fromAddr; addr < toAddr; addr += System::PAGE_SIZE)

src/emucore/CartEnhanced.hxx

@@ -214,6 +214,9 @@ class CartridgeEnhanced : public Cartridge
     // The mask for a bank segment
     uInt16 myBankMask{ROM_MASK};
 
+    // Usually myBankShift - 1
+    uInt16 myRamBankShift{0};
+
   protected:
     // The extra RAM size
     size_t myRamSize{RAM_SIZE};                 // default 0
@@ -318,7 +321,7 @@ class CartridgeEnhanced : public Cartridge
     virtual uInt16 getStartBank() const { return 0; }
 
     /**
-      Get the ROM offset of the segment of the given address
+      Get the ROM offset of the segment of the given address.
 
       @param address  The address to get the offset for
       @return  The calculated offset
@@ -328,14 +331,16 @@ class CartridgeEnhanced : public Cartridge
     }
 
     /**
-      Get the RAM offset of the segment of the given address
+      Get the RAM offset of the segment of the given address.
+      The RAM banks are half the size of a ROM bank.
 
       @param address  The address to get the offset for
       @return  The calculated offset
     */
     uInt16 ramAddressSegmentOffset(uInt16 address) const {
-      return static_cast<uInt16>((myCurrentSegOffset[
+      return static_cast<uInt16>(
-        ((address & ROM_MASK) >> myBankShift) % myBankSegs] - mySize) >> 1);
+        (myCurrentSegOffset[((address & ROM_MASK) >> myBankShift) % myBankSegs] - mySize) 
+        >> (myBankShift - myRamBankShift));
     }
 
   private:

src/emucore/CartGL.cxx

@@ -0,0 +1,133 @@
+//============================================================================
+//
+//   SSSS    tt          lll  lll
+//  SS  SS   tt           ll   ll
+//  SS     tttttt  eeee   ll   ll   aaaa
+//   SSSS    tt   ee  ee  ll   ll      aa
+//      SS   tt   eeeeee  ll   ll   aaaaa  --  "An Atari 2600 VCS Emulator"
+//  SS  SS   tt   ee      ll   ll  aa  aa
+//   SSSS     ttt  eeeee llll llll  aaaaa
+//
+// Copyright (c) 1995-2023 by Bradford W. Mott, Stephen Anthony
+// and the Stella Team
+//
+// See the file "License.txt" for information on usage and redistribution of
+// this file, and for a DISCLAIMER OF ALL WARRANTIES.
+//============================================================================
+
+#include "System.hxx"
+#include "CartGL.hxx"
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+CartridgeGL::CartridgeGL(const ByteBuffer& image, size_t size,
+                         string_view md5, const Settings& settings,
+                         size_t bsSize)
+  : CartridgeEnhanced(image, size, md5, settings, bsSize)
+{
+  myBankShift = myRamBankShift = BANK_SHIFT;
+  myRamSize = RAM_SIZE;
+  myRamBankCount = RAM_BANKS;
+
+  if(size == 4_KB + 2_KB) // ROM containing RAM data?
+  {
+    myInitialRAM = make_unique<uInt8[]>(2_KB);
+    // Copy the RAM image into a buffer for use in reset()
+    std::copy_n(image.get() + 4_KB, 2_KB, myInitialRAM.get());
+  }
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void CartridgeGL::reset()
+{
+  CartridgeEnhanced::reset();
+
+  // Initially bank 0 is mapped into all four segments
+  bank(0, 0);
+  bank(0, 1);
+  bank(0, 2);
+  bank(0, 3);
+  myBankChanged = true;
+
+  myOrgAccess = mySystem->getPageAccess(0x1fc0);
+
+  initializeRAM(myRAM.get(), myRamSize);
+  if(myInitialRAM != nullptr)
+  {
+    // Copy the RAM image into my RAM buffer
+    std::copy_n(myInitialRAM.get(), 2_KB, myRAM.get());
+  }
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void CartridgeGL::install(System& system)
+{
+  CartridgeEnhanced::install(system);
+
+  System::PageAccess access(this, System::PageAccessType::READ);
+
+  mySystem->setPageAccess(0x480, access);
+  mySystem->setPageAccess(0x580, access);
+  mySystem->setPageAccess(0x680, access);
+  mySystem->setPageAccess(0x880, access);
+  mySystem->setPageAccess(0x980, access);
+  mySystem->setPageAccess(0xc80, access);
+  mySystem->setPageAccess(0xd80, access);
+
+  myReadOffset = myWriteOffset = 0;
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+bool CartridgeGL::checkSwitchBank(uInt16 address, uInt8)
+{
+  int slice = -1;
+  bool control = false;
+
+  // Switch banks if necessary
+  switch(address & 0x1f80)
+  {
+    case 0x480:
+      slice = 0;
+      break;
+    case 0x580:
+      slice = 1;
+      break;
+    case 0x880:
+      slice = 2;
+      break;
+    case 0x980:
+      slice = 3;
+      break;
+    case 0xc80:
+      control = true;
+      break;
+  }
+  if(slice >= 0)
+  {
+    //const bool isWrite = address & 0x20; // could be checked, but not necessary for known GL ROMs
+    bank(address & 0xf, slice);
+    return true;
+  }
+  if(control)
+  {
+    myEnablePROM = (address & 0x30) == 0x30;
+    if(myEnablePROM)
+      mySystem->setPageAccess(0x1fc0, System::PageAccess(this, System::PageAccessType::READ));
+    else
+      mySystem->setPageAccess(0x1fc0, myOrgAccess);
+    return true;
+  }
+  return false;
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+uInt8 CartridgeGL::peek(uInt16 address)
+{
+  if(myEnablePROM && ((address & ADDR_MASK) >= 0x1fc0) && ((address & ADDR_MASK) <= 0x1fdf))
+  {
+    return 0; // sufficient for PROM check
+  }
+
+  checkSwitchBank(address, 0);
+
+  return myRWPRandomValues[address & 0xFF];
+}

src/emucore/CartGL.hxx

@@ -0,0 +1,134 @@
+//============================================================================
+//
+//   SSSS    tt          lll  lll
+//  SS  SS   tt           ll   ll
+//  SS     tttttt  eeee   ll   ll   aaaa
+//   SSSS    tt   ee  ee  ll   ll      aa
+//      SS   tt   eeeeee  ll   ll   aaaaa  --  "An Atari 2600 VCS Emulator"
+//  SS  SS   tt   ee      ll   ll  aa  aa
+//   SSSS     ttt  eeeee llll llll  aaaaa
+//
+// Copyright (c) 1995-2023 by Bradford W. Mott, Stephen Anthony
+// and the Stella Team
+//
+// See the file "License.txt" for information on usage and redistribution of
+// this file, and for a DISCLAIMER OF ALL WARRANTIES.
+//============================================================================
+
+#ifndef CARTRIDGEGL_HXX
+#define CARTRIDGEGL_HXX
+
+#include "CartEnhanced.hxx"
+#ifdef DEBUGGER_SUPPORT
+  #include "CartGLWidget.hxx"
+#endif
+#include "System.hxx"
+
+/**
+  Cartridge class used for the GameLine Master module. In this bankswitching 
+  scheme the 2600's 4K cartridge address space is broken into four 1K segments.
+  The desired 1K bank of the ROM or RAM is selected as follows:
+  - $0480 + x: 1st 1K segment
+  - $0580 + x: 2nd 1K segment
+  - $0880 + x: 3rd 1K segment
+  - $0980 + x: 4th 1K segment
+  Where x is defined as follows:
+  - bits 0..3: mapped 1K bank (0..3 = ROM bank, 4..f = RAM bank)
+  - bit 5: 0 = read, 1 = write (RAM only)
+  Initially bank 0 is mapped to all four segments.
+  The scheme supports 4K ROM and 2K RAM.
+
+  $0c80.. and $0d80.. control the modem (not implemented, except for PROM access).
+  
+  @author  Thomas Jentzsch
+*/
+class CartridgeGL : public CartridgeEnhanced
+{
+  friend class CartridgeGLWidget;
+
+  public:
+    /**
+      Create a new cartridge using the specified image
+
+      @param image     Pointer to the ROM image
+      @param size      The size of the ROM image
+      @param md5       The md5sum of the ROM image
+      @param settings  A reference to the various settings (read-only)
+      @param bsSize    The size specified by the bankswitching scheme
+    */
+    CartridgeGL(const ByteBuffer& image, size_t size, string_view md5,
+                const Settings& settings, size_t bsSize = 4_KB);
+    ~CartridgeGL() override = default;
+
+  public:
+    /**
+      Reset device to its power-on state
+    */
+    void reset() override;
+
+    /**
+      Install cartridge in the specified system.  Invoked by the system
+      when the cartridge is attached to it.
+
+      @param system The system the device should install itself in
+    */
+    void install(System& system) override;
+
+    /**
+      Get a descriptor for the device name (used in error checking).
+
+      @return The name of the object
+    */
+    string name() const override { return "CartridgeGL"; }
+
+  #ifdef DEBUGGER_SUPPORT
+    /**
+      Get debugger widget responsible for accessing the inner workings
+      of the cart.
+    */
+    CartDebugWidget* debugWidget(GuiObject* boss, const GUI::Font& lfont,
+        const GUI::Font& nfont, int x, int y, int w, int h) override
+    {
+      return new CartridgeGLWidget(boss, lfont, nfont, x, y, w, h, *this);
+    }
+  #endif
+
+  public:
+    /**
+      Get the byte at the specified address.
+
+      @return The byte at the specified address
+    */
+    uInt8 peek(uInt16 address) override;
+
+  private:
+    bool checkSwitchBank(uInt16 address, uInt8) override;
+
+  protected:
+    // log(ROM bank segment size) / log(2)
+    static constexpr uInt16 BANK_SHIFT = 10; // = 1K = 0x0400
+
+    // The number of RAM banks
+    static constexpr uInt16 RAM_BANKS = 12;
+
+    // RAM size
+    static constexpr size_t RAM_SIZE = RAM_BANKS << BANK_SHIFT; // = 12K;
+
+  private:
+    // Initial RAM data from the cart (doesn't always exist)
+    ByteBuffer myInitialRAM{nullptr};
+
+    bool myEnablePROM{false};
+
+    System::PageAccess myOrgAccess;
+
+  private:
+    // Following constructors and assignment operators not supported
+    CartridgeGL() = delete;
+    CartridgeGL(const CartridgeGL&) = delete;
+    CartridgeGL(CartridgeGL&&) = delete;
+    CartridgeGL& operator=(const CartridgeGL&) = delete;
+    CartridgeGL& operator=(CartridgeGL&&) = delete;
+};
+
+#endif

src/emucore/module.mk

@@ -46,6 +46,7 @@ MODULE_OBJS := \
 	src/emucore/CartFA2.o \
 	src/emucore/CartFC.o \
 	src/emucore/CartFE.o \
+	src/emucore/CartGL.o \
 	src/emucore/CartMDM.o \
 	src/emucore/CartMVC.o \
 	src/emucore/CartSB.o \

src/os/windows/Stella.vcxproj

@@ -911,6 +911,7 @@
     <ClCompile Include="..\..\debugger\gui\CartFEWidget.cxx">
       <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Debug-NoDebugger|x64'">true</ExcludedFromBuild>
     </ClCompile>
+    <ClCompile Include="..\..\debugger\gui\CartGLWidget.cxx" />
     <ClCompile Include="..\..\debugger\gui\CartMDMWidget.cxx">
       <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Debug-NoDebugger|x64'">true</ExcludedFromBuild>
     </ClCompile>
@@ -996,6 +997,7 @@
     <ClCompile Include="..\..\emucore\CartDFSC.cxx" />
     <ClCompile Include="..\..\emucore\CartFA2.cxx" />
     <ClCompile Include="..\..\emucore\CartFC.cxx" />
+    <ClCompile Include="..\..\emucore\CartGL.cxx" />
     <ClCompile Include="..\..\emucore\CartMDM.cxx" />
     <ClCompile Include="..\..\emucore\CartMVC.cxx" />
     <ClCompile Include="..\..\emucore\CartTVBoy.cxx" />
@@ -2223,6 +2225,7 @@
     <ClInclude Include="..\..\debugger\gui\CartFEWidget.hxx">
       <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Debug-NoDebugger|x64'">true</ExcludedFromBuild>
     </ClInclude>
+    <ClInclude Include="..\..\debugger\gui\CartGLWidget.hxx" />
     <ClInclude Include="..\..\debugger\gui\CartMDMWidget.hxx">
       <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Debug-NoDebugger|x64'">true</ExcludedFromBuild>
     </ClInclude>
@@ -2319,6 +2322,7 @@
     <ClInclude Include="..\..\emucore\CartDFSC.hxx" />
     <ClInclude Include="..\..\emucore\CartFA2.hxx" />
     <ClInclude Include="..\..\emucore\CartFC.hxx" />
+    <ClInclude Include="..\..\emucore\CartGL.hxx" />
     <ClInclude Include="..\..\emucore\CartMDM.hxx" />
     <ClInclude Include="..\..\emucore\CartMVC.hxx" />
     <ClInclude Include="..\..\emucore\CartTVBoy.hxx" />

src/os/windows/Stella.vcxproj.filters

@@ -1197,6 +1197,12 @@
     <ClCompile Include="..\..\debugger\TimerMap.cxx">
       <Filter>Source Files\debugger</Filter>
     </ClCompile>
+    <ClCompile Include="..\..\emucore\CartGL.cxx">
+      <Filter>Source Files\emucore</Filter>
+    </ClCompile>
+    <ClCompile Include="..\..\debugger\gui\CartGLWidget.cxx">
+      <Filter>Source Files\debugger\gui</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="..\..\common\bspf.hxx">
@@ -2441,6 +2447,12 @@
     <ClInclude Include="..\..\debugger\TimerMap.hxx">
       <Filter>Header Files\debugger</Filter>
     </ClInclude>
+    <ClInclude Include="..\..\emucore\CartGL.hxx">
+      <Filter>Header Files\emucore</Filter>
+    </ClInclude>
+    <ClInclude Include="..\..\debugger\gui\CartGLWidget.hxx">
+      <Filter>Header Files\debugger\gui</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <None Include="stella.ico">