diff --git a/src/mame/drivers/dec0.c b/src/mame/drivers/dec0.c
index 7e063a48c4f..b9933b20ab7 100644
--- a/src/mame/drivers/dec0.c
+++ b/src/mame/drivers/dec0.c
@@ -318,7 +318,7 @@ ADDRESS_MAP_END
 
 static ADDRESS_MAP_START( hippodrm_sub_map, AS_PROGRAM, 8, dec0_state )
 	AM_RANGE(0x000000, 0x00ffff) AM_ROM
-	AM_RANGE(0x180000, 0x1800ff) AM_READWRITE(hippodrm_shared_r, hippodrm_shared_w)
+	AM_RANGE(0x180000, 0x18001f) AM_RAM AM_SHARE("hippodrm_shared")
 	AM_RANGE(0x1a0000, 0x1a0007) AM_DEVWRITE("tilegen3", deco_bac06_device, pf_control0_8bit_packed_w)
 	AM_RANGE(0x1a0010, 0x1a001f) AM_DEVWRITE("tilegen3", deco_bac06_device, pf_control1_8bit_swap_w)
 	AM_RANGE(0x1a1000, 0x1a17ff) AM_DEVREADWRITE("tilegen3", deco_bac06_device, pf_data_8bit_swap_r, pf_data_8bit_swap_w)
diff --git a/src/mame/includes/dec0.h b/src/mame/includes/dec0.h
index 4f23746b955..ba3623db17c 100644
--- a/src/mame/includes/dec0.h
+++ b/src/mame/includes/dec0.h
@@ -10,6 +10,7 @@ public:
 		m_ram(*this, "ram"),
 		m_spriteram(*this, "spriteram"),
 		m_robocop_shared_ram(*this, "robocop_shared"),
+		m_hippodrm_shared_ram(*this, "hippodrm_shared"),
 		m_tilegen1(*this, "tilegen1"),
 		m_tilegen2(*this, "tilegen2"),
 		m_tilegen3(*this, "tilegen3"),
@@ -23,18 +24,17 @@ public:
 	required_shared_ptr<UINT16> m_ram;
 	required_shared_ptr<UINT16> m_spriteram;
 	optional_shared_ptr<UINT8> m_robocop_shared_ram;
+	optional_shared_ptr<UINT8> m_hippodrm_shared_ram;
 
 	optional_device<deco_bac06_device> m_tilegen1;
 	optional_device<deco_bac06_device> m_tilegen2;
 	optional_device<deco_bac06_device> m_tilegen3;
 	optional_device<deco_mxc06_device> m_spritegen;
 
-
 	int m_GAME;
 	int m_i8751_return;
 	int m_i8751_command;
 	int m_slyspy_state;
-	int m_share[0xff];
 	int m_hippodrm_msb;
 	int m_hippodrm_lsb;
 	UINT8 m_i8751_ports[4];
@@ -54,8 +54,6 @@ public:
 	DECLARE_READ16_MEMBER(midres_controls_r);
 	DECLARE_READ8_MEMBER(hippodrm_prot_r);
 	DECLARE_WRITE8_MEMBER(hippodrm_prot_w);
-	DECLARE_READ8_MEMBER(hippodrm_shared_r);
-	DECLARE_WRITE8_MEMBER(hippodrm_shared_w);
 	DECLARE_READ8_MEMBER(dec0_mcu_port_r);
 	DECLARE_WRITE8_MEMBER(dec0_mcu_port_w);
 	DECLARE_READ16_MEMBER(hippodrm_68000_share_r);
diff --git a/src/mame/machine/dec0.c b/src/mame/machine/dec0.c
index d67f85efa09..3a64d88be0d 100644
--- a/src/mame/machine/dec0.c
+++ b/src/mame/machine/dec0.c
@@ -106,27 +106,15 @@ WRITE8_MEMBER(dec0_state::hippodrm_prot_w)
 //logerror("6280 PC %06x - Wrote %06x to %04x\n",cpu_getpc(),data,offset+0x1d0000);
 }
 
-READ8_MEMBER(dec0_state::hippodrm_shared_r)
-{
-	return m_share[offset];
-}
-
-WRITE8_MEMBER(dec0_state::hippodrm_shared_w)
-{
-	m_share[offset]=data;
-}
-
 READ16_MEMBER(dec0_state::hippodrm_68000_share_r)
 {
 	if (offset==0) space.device().execute().yield(); /* A wee helper */
-	assert(offset >= 0 && offset < 0xff);
-	return m_share[offset]&0xff;
+	return m_hippodrm_shared_ram[offset]&0xff;
 }
 
 WRITE16_MEMBER(dec0_state::hippodrm_68000_share_w)
 {
-	assert(offset >= 0 && offset < 0xff);
-	m_share[offset]=data&0xff;
+	m_hippodrm_shared_ram[offset]=data&0xff;
 }
 
 /******************************************************************************/
@@ -359,7 +347,7 @@ void dec0_state::h6280_decrypt(const char *cputag)
 DRIVER_INIT_MEMBER(dec0_state,hippodrm)
 {
 	UINT8 *RAM = memregion("sub")->base();
-	m_maincpu->space(AS_PROGRAM).install_readwrite_handler(0x180000, 0x180fff, read16_delegate(FUNC(dec0_state::hippodrm_68000_share_r),this), write16_delegate(FUNC(dec0_state::hippodrm_68000_share_w),this));
+	m_maincpu->space(AS_PROGRAM).install_readwrite_handler(0x180000, 0x18003f, read16_delegate(FUNC(dec0_state::hippodrm_68000_share_r),this), write16_delegate(FUNC(dec0_state::hippodrm_68000_share_w),this));
 	m_maincpu->space(AS_PROGRAM).install_write_handler(0xffc800, 0xffcfff, write16_delegate(FUNC(dec0_state::sprite_mirror_w),this));
 
 	h6280_decrypt("sub");
@@ -374,7 +362,6 @@ DRIVER_INIT_MEMBER(dec0_state,hippodrm)
 DRIVER_INIT_MEMBER(dec0_state,slyspy)
 {
 	UINT8 *RAM = memregion("audiocpu")->base();
-
 	h6280_decrypt("audiocpu");
 
 	/* Slyspy sound cpu has some protection */