diff --git a/core/hw/naomi/naomi_cart.cpp b/core/hw/naomi/naomi_cart.cpp
index 5c4fc22aa..ab9b128b3 100644
--- a/core/hw/naomi/naomi_cart.cpp
+++ b/core/hw/naomi/naomi_cart.cpp
@@ -1023,9 +1023,26 @@ bool M2Cartridge::Read(u32 offset, u32 size, void* dst)
 		EMUERROR("Invalid read @ %08x\n", offset);
 		return false;
 	}
+	else if (!(RomPioOffset & 0x20000000))
+	{
+		// 4MB mode
+		offset = (offset & 0x103fffff) | ((offset & 0x07c00000) << 1);
+	}
 	return NaomiCartridge::Read(offset, size, dst);
 }
 
+void* M2Cartridge::GetDmaPtr(u32& size)
+{
+	if (RomPioOffset & 0x20000000)
+		return NaomiCartridge::GetDmaPtr(size);
+
+	// 4MB mode
+	u32 offset4mb = (DmaOffset & 0x103fffff) | ((DmaOffset & 0x07c00000) << 1);
+	size = min(min(size, 0x400000 - (offset4mb & 0x3FFFFF)), RomSize - offset4mb);
+
+	return GetPtr(offset4mb, size);
+}
+
 bool M2Cartridge::Write(u32 offset, u32 size, u32 data)
 {
 	if (offset & 0x40000000)
diff --git a/core/hw/naomi/naomi_cart.h b/core/hw/naomi/naomi_cart.h
index 860e33ef0..19f4314ff 100644
--- a/core/hw/naomi/naomi_cart.h
+++ b/core/hw/naomi/naomi_cart.h
@@ -35,12 +35,12 @@ class NaomiCartridge : public Cartridge
 public:
 	NaomiCartridge(u32 size) : Cartridge(size), RomPioOffset(0), RomPioAutoIncrement(0), DmaOffset(0), DmaCount(0xffff) {}
 
-	virtual u32 ReadMem(u32 address, u32 size);
-	virtual void WriteMem(u32 address, u32 data, u32 size);
-	virtual void* GetDmaPtr(u32 &size);
-	virtual void AdvancePtr(u32 size);
-	virtual void Serialize(void** data, unsigned int* total_size);
-	virtual void Unserialize(void** data, unsigned int* total_size);
+	virtual u32 ReadMem(u32 address, u32 size) override;
+	virtual void WriteMem(u32 address, u32 data, u32 size) override;
+	virtual void* GetDmaPtr(u32 &size) override;
+	virtual void AdvancePtr(u32 size) override;
+	virtual void Serialize(void** data, unsigned int* total_size) override;
+	virtual void Unserialize(void** data, unsigned int* total_size) override;
 
 	void SetKey(u32 key) override { this->key = key; }
 
@@ -66,11 +66,12 @@ class M2Cartridge : public NaomiCartridge
 public:
 	M2Cartridge(u32 size) : NaomiCartridge(size) {}
 
-	virtual bool Read(u32 offset, u32 size, void* dst);
-	virtual bool Write(u32 offset, u32 size, u32 data);
+	virtual bool Read(u32 offset, u32 size, void* dst) override;
+	virtual bool Write(u32 offset, u32 size, u32 data) override;
 	u16 ReadCipheredData(u32 offset);
-	virtual void Serialize(void** data, unsigned int* total_size);
-	virtual void Unserialize(void** data, unsigned int* total_size);
+	virtual void Serialize(void** data, unsigned int* total_size) override;
+	virtual void Unserialize(void** data, unsigned int* total_size) override;
+	virtual void* GetDmaPtr(u32& size) override;
 
 private:
 	u8 naomi_cart_ram[64 * 1024];