diff --git a/src/mess/drivers/a7800.c b/src/mess/drivers/a7800.c
index 14ac1157f90..c8e7efcdda7 100644
--- a/src/mess/drivers/a7800.c
+++ b/src/mess/drivers/a7800.c
@@ -1033,7 +1033,7 @@ static MACHINE_CONFIG_START( a7800_ntsc, a7800_state )
 
 	/* video hardware */
 	MCFG_SCREEN_ADD("screen", RASTER)
-	MCFG_SCREEN_RAW_PARAMS( 7159090, 456, 0, 320, 262, 26, 26 + 192 + 30 )
+	MCFG_SCREEN_RAW_PARAMS( 7159090, 456, 0, 320, 263, 26, 26 + 192 + 30 )
 	MCFG_SCREEN_UPDATE_DRIVER(a7800_state, screen_update_a7800)
 	MCFG_SCREEN_PALETTE("palette")
 
@@ -1072,7 +1072,7 @@ static MACHINE_CONFIG_DERIVED( a7800_pal, a7800_ntsc )
 //  MCFG_TIMER_ADD_SCANLINE("scantimer", a7800_interrupt, "screen", 0, 1)
 
 	MCFG_SCREEN_MODIFY( "screen" )
-		MCFG_SCREEN_RAW_PARAMS( 7093788, 456, 0, 320, 312, 34, 34 + 228 + 30 )
+		MCFG_SCREEN_RAW_PARAMS( 7093788, 456, 0, 320, 313, 34, 34 + 228 + 30 )
 
 	MCFG_PALETTE_MODIFY("palette")
 	MCFG_PALETTE_INIT_OWNER(a7800_state, a7800p )
@@ -1099,7 +1099,7 @@ MACHINE_CONFIG_END
 
 ROM_START( a7800 )
 	ROM_REGION(0x100000, "maincpu", 0)
-	ROM_FILL(0x0000, 0x40000, 0xff)
+	ROM_FILL(0x0000, 0x100000, 0xff)
 	ROM_SYSTEM_BIOS( 0, "a7800", "Atari 7800" )
 	ROMX_LOAD("7800.u7", 0xf000, 0x1000, CRC(5d13730c) SHA1(d9d134bb6b36907c615a594cc7688f7bfcef5b43), ROM_BIOS(1))
 	ROM_SYSTEM_BIOS( 1, "a7800pr", "Atari 7800 (prototype with Asteroids)" )
@@ -1108,7 +1108,7 @@ ROM_END
 
 ROM_START( a7800p )
 	ROM_REGION(0x100000, "maincpu", 0)
-	ROM_FILL(0x0000, 0x40000, 0xff)
+	ROM_FILL(0x0000, 0x100000, 0xff)
 	ROM_LOAD("7800pal.rom", 0xc000, 0x4000, CRC(d5b61170) SHA1(5a140136a16d1d83e4ff32a19409ca376a8df874))
 ROM_END
 
diff --git a/src/mess/machine/a7800.c b/src/mess/machine/a7800.c
index 218a73d04bb..107cd0dcc69 100644
--- a/src/mess/machine/a7800.c
+++ b/src/mess/machine/a7800.c
@@ -107,13 +107,13 @@ void a7800_state::a7800_driver_init(int ispal, int lines)
 
 DRIVER_INIT_MEMBER(a7800_state,a7800_ntsc)
 {
-	a7800_driver_init(FALSE, 262);
+	a7800_driver_init(FALSE, 263);
 }
 
 
 DRIVER_INIT_MEMBER(a7800_state,a7800_pal)
 {
-	a7800_driver_init(TRUE, 312);
+	a7800_driver_init(TRUE, 313);
 }
 
 
@@ -520,11 +520,13 @@ READ8_MEMBER(a7800_state::a7800_TIA_r)
 
 WRITE8_MEMBER(a7800_state::a7800_TIA_w)
 {
-	switch(offset) {
-	case 0x01:
+	if (offset<0x20) { //INPTCTRL covers TIA registers 0x00-0x1F until locked
 		if(data & 0x01)
 		{
-			m_maria_flag=1;
+			if ((m_ctrl_lock)&&(offset==0x01))
+				m_maria_flag=1;
+			else if (!m_ctrl_lock)
+				m_maria_flag=1;
 		}
 		if(!m_ctrl_lock)
 		{
@@ -536,7 +538,6 @@ WRITE8_MEMBER(a7800_state::a7800_TIA_w)
 			else
 				memcpy( m_ROM + 0xC000, m_bios_bkup, 0x4000 );
 		}
-		break;
 	}
 	m_tia->tia_sound_w(space, offset, data);
 	m_ROM[offset] = data;
diff --git a/src/mess/video/a7800.c b/src/mess/video/a7800.c
index f050ba60eea..67e96322092 100644
--- a/src/mess/video/a7800.c
+++ b/src/mess/video/a7800.c
@@ -126,7 +126,6 @@ void a7800_state::maria_draw_scanline()
 	int x, d, c, i, pixel_cell, cells;
 	int maria_cycles;
 
-	//maria_cycles = 0;
      if ( m_maria_offset == 0 )
              maria_cycles = 5+19; // DMA startup + last line shutdown
 	 else
@@ -173,10 +172,10 @@ void a7800_state::maria_draw_scanline()
 			if (ind)
 			{
 				c = READ_MEM(graph_adr + x) & 0xFF;
-				maria_cycles += 3;
 				data_addr = (m_maria_charbase | c) + (m_maria_offset << 8);
 				if (is_holey(data_addr))
 					continue;
+				maria_cycles += 3;
 				if( m_maria_cwidth ) // two data bytes per map byte
 				{
 					cells = write_line_ram(data_addr, hpos, pal);
@@ -262,7 +261,7 @@ TIMER_DEVICE_CALLBACK_MEMBER(a7800_state::a7800_interrupt)
 	if (frame_scanline == 16)
 		m_maria_vblank = 0x00;
 
-	if ( frame_scanline == ( m_lines - 4 ) )
+	if ( frame_scanline == ( m_lines - 5 ) )
 	{
 		m_maria_vblank = 0x80;
 	}
@@ -286,12 +285,11 @@ TIMER_CALLBACK_MEMBER(a7800_state::a7800_maria_startdma)
 		m_maria_offset = READ_MEM(m_maria_dll) & 0x0f;
 		m_maria_holey = (READ_MEM(m_maria_dll) & 0x60) >> 5;
 		m_maria_nmi = READ_MEM(m_maria_dll) & 0x80;
-		m_maincpu->eat_cycles(6); // 24 Maria cycles minimum (DMA startup + shutdown list-list fetch)
 		/*  logerror("DLL=%x\n",m_maria_dll); */
 	}
 
 
-	if( ( frame_scanline > 15 ) && (frame_scanline < (m_lines - 4)) && m_maria_dmaon )
+	if( ( frame_scanline > 15 ) && (frame_scanline < (m_lines - 5)) && m_maria_dmaon )
 	{
 		maria_draw_scanline();
 
@@ -301,7 +299,6 @@ TIMER_CALLBACK_MEMBER(a7800_state::a7800_maria_startdma)
 			m_maria_dl = (READ_MEM(m_maria_dll+1) << 8) | READ_MEM(m_maria_dll+2);
 			m_maria_offset = READ_MEM(m_maria_dll) & 0x0f;
 			m_maria_holey = (READ_MEM(m_maria_dll) & 0x60) >> 5;
-			m_maincpu->eat_cycles(5); // 20 Maria cycles (DMA startup + shutdown)
 			if ( READ_MEM(m_maria_dll & 0x10) )
 				logerror("dll bit 5 set!\n");
 			m_maria_nmi = READ_MEM(m_maria_dll) & 0x80;