this should fix the resets and lockups (at least most of them). sram is still not saved, though... nw.

hash/megadriv.xml

@@ -26138,7 +26138,7 @@ Notice that these are not working on real hardware due to bugged code with VDP i
 		<year>2005</year>
 		<publisher>Super Fighter Team</publisher>
 		<part name="cart" interface="megadriv_cart">
-			<feature name="slot" value="rom_beggar" />
+			<feature name="slot" value="rom_beggarp" />
 			<dataarea name="rom" size="4194304">
 				<rom name="beggar prince (unl).bin" size="4194304" crc="f3af46cd" sha1="f481b970756c482d8f408c4bab8902172837e7d8" offset="000000" loadflag="load16_word_swap" />
 			</dataarea>
@@ -26150,7 +26150,7 @@ Notice that these are not working on real hardware due to bugged code with VDP i
 		<year>1996</year>
 		<publisher>C&amp;E</publisher>
 		<part name="cart" interface="megadriv_cart">
-			<feature name="slot" value="rom_beggar" />
+			<feature name="slot" value="rom_xinqig" />
 			<dataarea name="rom" size="4194304">
 				<rom name="xin qi gai wang zi (chi) (alt) (unl).bin" size="4194304" crc="da5a4bfe" sha1="75f8003a6388814c1880347882b244549da62158" offset="000000" loadflag="load16_word_swap" />
 			</dataarea>
@@ -26162,7 +26162,7 @@ Notice that these are not working on real hardware due to bugged code with VDP i
 		<year>1996</year>
 		<publisher>C&amp;E</publisher>
 		<part name="cart" interface="megadriv_cart">
-			<feature name="slot" value="rom_beggar" />
+			<feature name="slot" value="rom_xinqig" />
 			<dataarea name="rom" size="4194304">
 				<rom name="xin qi gai wang zi (chi) (unl).bin" size="4194304" crc="dd2f38b5" sha1="4a7494d8601149f43ba7e3595a0b2340cde2e9ba" offset="000000" loadflag="load16_word_swap" />
 			</dataarea>

src/mess/drivers/megadriv.c

@@ -304,7 +304,8 @@ static SLOT_INTERFACE_START(md_cart)
 	SLOT_INTERFACE_INTERNAL("rom_sramsafe",  MD_ROM_SRAM)
 	SLOT_INTERFACE_INTERNAL("rom_fram",  MD_ROM_FRAM)
 	SLOT_INTERFACE_INTERNAL("rom_hardbl95", MD_ROM_SRAM)
-	SLOT_INTERFACE_INTERNAL("rom_beggar",  MD_ROM_SRAM)
+	SLOT_INTERFACE_INTERNAL("rom_xinqig",  MD_ROM_SRAM)
+	SLOT_INTERFACE_INTERNAL("rom_beggarp",  MD_ROM_BEGGARP)
 	SLOT_INTERFACE_INTERNAL("rom_wukong",  MD_ROM_WUKONG)
 // EEPROM handling (not supported fully yet)
 	SLOT_INTERFACE_INTERNAL("rom_eeprom",  MD_STD_EEPROM)

src/mess/machine/md_rom.c

@@ -48,6 +48,7 @@ const device_type MD_ROM_REDCL = &device_creator<md_rom_redcl_device>;
 const device_type MD_ROM_SQUIR = &device_creator<md_rom_squir_device>;
 const device_type MD_ROM_TOPF = &device_creator<md_rom_topf_device>;
 const device_type MD_ROM_RADICA = &device_creator<md_rom_radica_device>;
+const device_type MD_ROM_BEGGARP = &device_creator<md_rom_beggarp_device>;
 const device_type MD_ROM_WUKONG = &device_creator<md_rom_wukong_device>;
 
 
@@ -193,6 +194,11 @@ md_rom_radica_device::md_rom_radica_device(const machine_config &mconfig, const
 {
 }
 
+md_rom_beggarp_device::md_rom_beggarp_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock)
+					: md_std_rom_device(mconfig, MD_ROM_BEGGARP, "MD Beggar Prince", tag, owner, clock)
+{
+}
+
 md_rom_wukong_device::md_rom_wukong_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock)
 					: md_std_rom_device(mconfig, MD_ROM_WUKONG, "MD Legend of Wukong", tag, owner, clock)
 {
@@ -292,6 +298,14 @@ void md_rom_radica_device::device_start()
 	save_item(NAME(m_bank));
 }
 
+void md_rom_beggarp_device::device_start()
+{
+	m_mode = 0;
+	m_lock = 0;
+	save_item(NAME(m_mode));
+	save_item(NAME(m_lock));
+}
+
 void md_rom_wukong_device::device_start()
 {
 	m_mode = 0;
@@ -1055,6 +1069,70 @@ READ16_MEMBER(md_rom_radica_device::read_a13)
 	return 0;
 }
 
+/*-------------------------------------------------
+ BEGGAR PRINCE
+ This game uses cart which is the same as SEGA_SRAM 
+ + bankswitch mechanism to remap some 256K chunk of
+ ROM and to enable/disable SRAM (not yet fully 
+ emulated)
+ -------------------------------------------------*/
+
+READ16_MEMBER(md_rom_beggarp_device::read)
+{
+	if (m_mode & 2)
+	{
+		//000000-03ffff = ROM bank 15 x 256k
+		//040000-3bffff = ROM banks 2 to 15 x256k
+		//3c0000-3fffff = ?? SRAM ?? (32k?)
+		if (offset < 0x040000/2)
+			return m_rom[offset + 0x380000/2];
+		else if (offset >= m_nvram_start/2 && offset <= m_nvram_end/2 && m_nvram_active)
+			return m_nvram[offset & 0x3fff];
+		else if (offset < 0x400000/2)
+			return m_rom[offset & 0x1fffff];
+	}
+	else
+	{
+		// currently not supported
+		//		if (m_mode & 1)	//00-40 = unmapped (open bus?)
+		
+ 		//00-40 = ROM banks 1 to 16 x256k
+		if (offset < 0x400000/2)
+			return m_rom[offset & 0x1fffff];
+	}
+	
+	return 0xffff;
+}
+
+WRITE16_MEMBER(md_rom_beggarp_device::write)
+{
+	if (offset >= 0x0e00/2 && offset < 0x0f00/2)	// it actually writes to 0xe00/2
+	{
+		if (!m_lock)
+			m_mode = (data & 0xc0) >> 6;
+		
+		m_lock = BIT(data, 5); // lock bankswitch hardware when set, until hard reset
+	}
+	
+	// SRAM is only accessible in mode 2
+	if (offset >= m_nvram_start/2 && offset <= m_nvram_end/2 && m_nvram_active && !m_nvram_readonly && m_mode == 2)
+		m_nvram[offset & 0x3fff] = data;
+}
+
+WRITE16_MEMBER(md_rom_beggarp_device::write_a13)
+{
+	if (offset == 0xf0/2)
+	{
+		/* unsure if this is actually supposed to toggle or just switch on? yet to encounter game that uses this */
+		m_nvram_active = BIT(data, 0);
+		m_nvram_readonly = BIT(data, 1);
+		
+		// since a lot of generic carts ends up here if loaded from fullpath
+		// we turn on nvram (with m_nvram_handlers_installed) only if they toggle it on by writing here!
+		if (m_nvram_active)
+			m_nvram_handlers_installed = 1;
+	}
+}
 
 /*-------------------------------------------------
  LEGEND OF WUKONG 

src/mess/machine/md_rom.h

@@ -483,6 +483,26 @@ private:
 	UINT8 m_bank;
 };
 
+// ======================> md_rom_beggarp_device
+
+class md_rom_beggarp_device : public md_std_rom_device
+{
+public:
+	// construction/destruction
+	md_rom_beggarp_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock);
+	
+	// device-level overrides
+	virtual void device_start();
+	virtual void device_config_complete() { m_shortname = "md_rom_beggarp"; }
+	
+	// reading and writing
+	virtual DECLARE_READ16_MEMBER(read);
+	virtual DECLARE_WRITE16_MEMBER(write);
+	virtual DECLARE_WRITE16_MEMBER(write_a13);
+
+	UINT8 m_mode, m_lock;
+};
+
 // ======================> md_rom_wukong_device
 
 class md_rom_wukong_device : public md_std_rom_device
@@ -533,6 +553,7 @@ extern const device_type MD_ROM_SSF2;
 extern const device_type MD_ROM_SQUIR;
 extern const device_type MD_ROM_TOPF;
 extern const device_type MD_ROM_RADICA;
+extern const device_type MD_ROM_BEGGARP;
 extern const device_type MD_ROM_WUKONG;
 
 #endif

src/mess/machine/md_slot.c

@@ -240,7 +240,8 @@ static const md_slot slot_list[] =
 	{ SEGA_SRAM, "rom_sram" },
 	{ SEGA_FRAM, "rom_fram" },
 	{ HARDBALL95, "rom_hardbl95" },
-	{ BEGGAR, "rom_beggar"},
+	{ XINQIG, "rom_xinqig"},
+	{ BEGGARP, "rom_beggarp"},
 	{ WUKONG, "rom_wukong"},
 
 	{ SEGA_EEPROM, "rom_eeprom" },
@@ -633,13 +634,19 @@ void base_md_cart_slot_device::setup_nvram()
 			m_cart->m_nvram_active = 1;
 			m_cart->m_nvram_handlers_installed = 1;
 			break;
-		case BEGGAR:
+		case XINQIG:
 			m_cart->m_nvram_start = 0x400000;
 			m_cart->m_nvram_end = m_cart->m_nvram_start + 0xffff;
 			m_cart->nvram_alloc(machine(), m_cart->m_nvram_end - m_cart->m_nvram_start + 1);
 			m_cart->m_nvram_active = 1;
 			m_cart->m_nvram_handlers_installed = 1;
 			break;
+		case BEGGARP:
+			m_cart->m_nvram_start = 0x3c0000;
+			m_cart->m_nvram_end = m_cart->m_nvram_start + 0xffff;
+			m_cart->nvram_alloc(machine(), 0x8000);	// 32K mirrored
+			m_cart->m_nvram_active = 1;
+			break;
 		case WUKONG:
 			m_cart->m_nvram_start = 0x3c0000;
 			m_cart->m_nvram_end = m_cart->m_nvram_start + 0x3fff;

src/mess/machine/md_slot.h

@@ -21,7 +21,8 @@ enum
 	// Cart + NVRAM
 	SEGA_SRAM, SEGA_FRAM,
 	HARDBALL95,                  /* Hardball 95 uses different sram start address */
-	BEGGAR,                      /* Beggar Prince / Xin Qigai Wangzi uses different sram start address and has no valid header */
+	XINQIG,                   /* Xin Qigai Wangzi uses different sram start address and has no valid header */
+	BEGGARP,                     /* Beggar Prince uses different sram start address + bankswitch tricks */
 	WUKONG,                      /* Legend of Wukong uses different sram start address + bankswitch trick for last 128K of ROM */
 
 	// EEPROM