diff --git a/Assets/dll/gpgx.wbx.zst b/Assets/dll/gpgx.wbx.zst
index c30aa68375..1e6d7db00c 100644
Binary files a/Assets/dll/gpgx.wbx.zst and b/Assets/dll/gpgx.wbx.zst differ
diff --git a/waterbox/gpgx/core/mem68k.c b/waterbox/gpgx/core/mem68k.c
index fa5c52d23e..2957d0e0f0 100644
--- a/waterbox/gpgx/core/mem68k.c
+++ b/waterbox/gpgx/core/mem68k.c
@@ -658,6 +658,8 @@ void ctrl_io_write_byte(unsigned int address, unsigned int data)
 
           case 0x01:  /* SUB-CPU control */
           {
+            unsigned int halted = s68k.stopped;
+
             /* RESET bit */
             if (data & 0x01)
             {
@@ -686,6 +688,40 @@ void ctrl_io_write_byte(unsigned int address, unsigned int data)
               s68k_pulse_halt();
             }
 
+            /* check if SUB-CPU halt status has changed */
+            if (s68k.stopped != halted)
+            {
+              int i;
+
+              /* PRG-RAM can only be accessed from MAIN 68K & Z80 when SUB-CPU is halted (Dungeon Explorer USA version) */
+              if ((data & 0x03) != 0x01)
+              {
+                /* $020000-$03FFFF (resp. $420000-$43FFFF) is mapped to PRG-RAM 128K bank (mirrored every 256 KB) */
+                for (i=scd.cartridge.boot+0x02; i<scd.cartridge.boot+0x20; i+=4)
+                {
+                  m68k.memory_map[i].read8   = m68k.memory_map[i+1].read8   = NULL;
+                  m68k.memory_map[i].read16  = m68k.memory_map[i+1].read16  = NULL;
+                  m68k.memory_map[i].write8  = m68k.memory_map[i+1].write8  = NULL;
+                  m68k.memory_map[i].write16 = m68k.memory_map[i+1].write16 = NULL;
+                  zbank_memory_map[i].read   = zbank_memory_map[i+1].read   = NULL;
+                  zbank_memory_map[i].write  = zbank_memory_map[i+1].write  = NULL;
+                }
+              }
+              else
+              {
+                /* $020000-$03FFFF (resp. $420000-$43FFFF) is not mapped (mirrored every 256 KB) */
+                for (i=scd.cartridge.boot+0x02; i<scd.cartridge.boot+0x20; i+=4)
+                {
+                  m68k.memory_map[i].read8   = m68k.memory_map[i+1].read8   = m68k_read_bus_8;
+                  m68k.memory_map[i].read16  = m68k.memory_map[i+1].read16  = m68k_read_bus_16;
+                  m68k.memory_map[i].write8  = m68k.memory_map[i+1].write8  = m68k_unused_8_w;
+                  m68k.memory_map[i].write16 = m68k.memory_map[i+1].write16 = m68k_unused_16_w;
+                  zbank_memory_map[i].read   = zbank_memory_map[i+1].read   = zbank_unused_r;
+                  zbank_memory_map[i].write  = zbank_memory_map[i+1].write  = zbank_unused_w;
+                }
+              }
+            }
+
             scd.regs[0x00].byte.l = data;
             return;
           }
@@ -854,6 +890,8 @@ void ctrl_io_write_word(unsigned int address, unsigned int data)
         {
           case 0x00:  /* SUB-CPU interrupt & control */
           {
+            unsigned int halted = s68k.stopped;
+
             /* RESET bit */
             if (data & 0x01)
             {
@@ -882,6 +920,40 @@ void ctrl_io_write_word(unsigned int address, unsigned int data)
               s68k_pulse_halt();
             }
 
+            /* check if SUB-CPU halt status has changed */
+            if (s68k.stopped != halted)
+            {
+              int i;
+
+              /* PRG-RAM can only be accessed from MAIN 68K & Z80 when SUB-CPU is halted (Dungeon Explorer USA version) */
+              if ((data & 0x03) != 0x01)
+              {
+                /* $020000-$03FFFF (resp. $420000-$43FFFF) is mapped to PRG-RAM 128K bank (mirrored every 256 KB) */
+                for (i=scd.cartridge.boot+0x02; i<scd.cartridge.boot+0x20; i+=4)
+                {
+                  m68k.memory_map[i].read8   = m68k.memory_map[i+1].read8   = NULL;
+                  m68k.memory_map[i].read16  = m68k.memory_map[i+1].read16  = NULL;
+                  m68k.memory_map[i].write8  = m68k.memory_map[i+1].write8  = NULL;
+                  m68k.memory_map[i].write16 = m68k.memory_map[i+1].write16 = NULL;
+                  zbank_memory_map[i].read   = zbank_memory_map[i+1].read   = NULL;
+                  zbank_memory_map[i].write  = zbank_memory_map[i+1].write  = NULL;
+                }
+              }
+              else
+              {
+                /* $020000-$03FFFF (resp. $420000-$43FFFF) is not mapped (mirrored every 256 KB) */
+                for (i=scd.cartridge.boot+0x02; i<scd.cartridge.boot+0x20; i+=4)
+                {
+                  m68k.memory_map[i].read8   = m68k.memory_map[i+1].read8   = m68k_read_bus_8;
+                  m68k.memory_map[i].read16  = m68k.memory_map[i+1].read16  = m68k_read_bus_16;
+                  m68k.memory_map[i].write8  = m68k.memory_map[i+1].write8  = m68k_unused_8_w;
+                  m68k.memory_map[i].write16 = m68k.memory_map[i+1].write16 = m68k_unused_16_w;
+                  zbank_memory_map[i].read   = zbank_memory_map[i+1].read   = zbank_unused_r;
+                  zbank_memory_map[i].write  = zbank_memory_map[i+1].write  = zbank_unused_w;
+                }
+              }
+            }
+
             /* IFL2 bit */
             if (data & 0x100)
             {