diff --git a/src/mame/drivers/cardline.c b/src/mame/drivers/cardline.c
index 8f2dd4c5bad..2eda29b5910 100644
--- a/src/mame/drivers/cardline.c
+++ b/src/mame/drivers/cardline.c
@@ -139,7 +139,8 @@ WRITE_LINE_MEMBER(cardline_state::hsync_changed)
 {
 	/* update any video up to the current scanline */
 	m_hsync_q = (state ? 0x00 : 0x10);
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
 }
 
 WRITE_LINE_MEMBER(cardline_state::vsync_changed)
diff --git a/src/mame/drivers/cubeqst.c b/src/mame/drivers/cubeqst.c
index d11cf9ead2a..837e77c9a9f 100644
--- a/src/mame/drivers/cubeqst.c
+++ b/src/mame/drivers/cubeqst.c
@@ -101,7 +101,9 @@ void cubeqst_state::video_start()
 
 WRITE16_MEMBER(cubeqst_state::palette_w)
 {
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
+
 	COMBINE_DATA(&m_generic_paletteram_16[offset]);
 }
 
diff --git a/src/mame/drivers/firefox.c b/src/mame/drivers/firefox.c
index 7d18687fed4..d77ee4b6a39 100644
--- a/src/mame/drivers/firefox.c
+++ b/src/mame/drivers/firefox.c
@@ -267,7 +267,8 @@ UINT32 firefox_state::screen_update_firefox(screen_device &screen, bitmap_rgb32
 
 TIMER_DEVICE_CALLBACK_MEMBER(firefox_state::video_timer_callback)
 {
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
 
 	m_maincpu->set_input_line(M6809_IRQ_LINE, ASSERT_LINE );
 }
diff --git a/src/mame/drivers/galaxian.c b/src/mame/drivers/galaxian.c
index bcd1651c2c7..446e3b310b7 100644
--- a/src/mame/drivers/galaxian.c
+++ b/src/mame/drivers/galaxian.c
@@ -5235,7 +5235,8 @@ TIMER_DEVICE_CALLBACK_MEMBER(galaxian_state::timefgtr_scanline)
 	// change spriteram base per each 64-line part of the screen
 	if ((split & 0x3f) == 0)
 	{
-		m_screen->update_now();
+//		m_screen->update_now();
+		m_screen->update_partial(m_screen->vpos());
 		m_sprites_base = 0x40 | (split << 2 & 0x300);
 	}
 }
diff --git a/src/mame/drivers/merit.c b/src/mame/drivers/merit.c
index 7131d099cc5..2983b49aeac 100644
--- a/src/mame/drivers/merit.c
+++ b/src/mame/drivers/merit.c
@@ -232,7 +232,8 @@ WRITE8_MEMBER(merit_state::palette_w)
 {
 	int co;
 
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
 	data &= 0x0f;
 
 	co = ((m_ram_attr[offset] & 0x7F) << 3) | (offset & 0x07);
@@ -305,7 +306,8 @@ MC6845_UPDATE_ROW( merit_state::crtc_update_row )
 WRITE_LINE_MEMBER(merit_state::hsync_changed)
 {
 	/* update any video up to the current scanline */
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
 }
 
 WRITE_LINE_MEMBER(merit_state::vsync_changed)
diff --git a/src/mame/drivers/segas24.c b/src/mame/drivers/segas24.c
index 7a3a5f76a51..34be9d6ba5d 100644
--- a/src/mame/drivers/segas24.c
+++ b/src/mame/drivers/segas24.c
@@ -878,8 +878,11 @@ TIMER_DEVICE_CALLBACK_MEMBER(segas24_state::irq_timer_cb)
 	if(irq_allow1 & (1 << IRQ_TIMER))
 		m_subcpu->set_input_line(IRQ_TIMER+1, ASSERT_LINE);
 
-	if(irq_tmode == 1 || irq_tmode == 2)
-		m_screen->update_now();
+	if (irq_tmode == 1 || irq_tmode == 2)
+	{
+	//	m_screen->update_now();
+		m_screen->update_partial(m_screen->vpos());
+	}
 }
 
 TIMER_DEVICE_CALLBACK_MEMBER(segas24_state::irq_timer_clear_cb)
diff --git a/src/mame/drivers/slotcarn.c b/src/mame/drivers/slotcarn.c
index c5f0726a886..b1cedc60b39 100644
--- a/src/mame/drivers/slotcarn.c
+++ b/src/mame/drivers/slotcarn.c
@@ -82,7 +82,8 @@ WRITE8_MEMBER(slotcarn_state::palette_w)
 {
 	int co;
 
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
 	data &= 0x0f;
 
 	co = ((m_ram_attr[offset] & 0x7F) << 3) | (offset & 0x07);
@@ -157,7 +158,8 @@ MC6845_UPDATE_ROW( slotcarn_state::crtc_update_row )
 WRITE_LINE_MEMBER(slotcarn_state::hsync_changed)
 {
 	/* update any video up to the current scanline */
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
 }
 
 WRITE_LINE_MEMBER(slotcarn_state::vsync_changed)
diff --git a/src/mame/drivers/vicdual.c b/src/mame/drivers/vicdual.c
index 73e7682a86e..d180791cf48 100644
--- a/src/mame/drivers/vicdual.c
+++ b/src/mame/drivers/vicdual.c
@@ -207,14 +207,16 @@ int vicdual_state::is_cabinet_color()
 
 WRITE8_MEMBER(vicdual_state::videoram_w)
 {
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
 	m_videoram[offset] = data;
 }
 
 
 WRITE8_MEMBER(vicdual_state::characterram_w)
 {
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
 	m_characterram[offset] = data;
 }
 
diff --git a/src/mame/video/btoads.c b/src/mame/video/btoads.c
index 8dbdec15400..7bbbfbcd014 100644
--- a/src/mame/video/btoads.c
+++ b/src/mame/video/btoads.c
@@ -93,7 +93,8 @@ WRITE16_MEMBER( btoads_state::display_control_w )
 WRITE16_MEMBER( btoads_state::scroll0_w )
 {
 	/* allow multiple changes during display */
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
 
 	/* upper bits are Y scroll, lower bits are X scroll */
 	if (ACCESSING_BITS_8_15)
@@ -106,7 +107,8 @@ WRITE16_MEMBER( btoads_state::scroll0_w )
 WRITE16_MEMBER( btoads_state::scroll1_w )
 {
 	/* allow multiple changes during display */
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
 
 	/* upper bits are Y scroll, lower bits are X scroll */
 	if (ACCESSING_BITS_8_15)
diff --git a/src/mame/video/cloak.c b/src/mame/video/cloak.c
index f9138f25970..18551ff6b52 100644
--- a/src/mame/video/cloak.c
+++ b/src/mame/video/cloak.c
@@ -92,7 +92,9 @@ void cloak_state::set_current_bitmap_videoram_pointer()
 
 WRITE8_MEMBER(cloak_state::cloak_clearbmp_w)
 {
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
+
 	m_bitmap_videoram_selected = data & 0x01;
 	set_current_bitmap_videoram_pointer();
 
diff --git a/src/mame/video/dkong.c b/src/mame/video/dkong.c
index 1f8e700a2f1..484be075692 100644
--- a/src/mame/video/dkong.c
+++ b/src/mame/video/dkong.c
@@ -876,7 +876,8 @@ TIMER_CALLBACK_MEMBER(dkong_state::scanline_callback)
 		radarscp_scanline(scanline);
 
 	/* update any video up to the current scanline */
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
 
 	scanline = (scanline+1) % VTOTAL;
 	/* come back at the next appropriate scanline */
diff --git a/src/mame/video/galaxian.c b/src/mame/video/galaxian.c
index ce800e92a83..1e84b9b0a9a 100644
--- a/src/mame/video/galaxian.c
+++ b/src/mame/video/galaxian.c
@@ -480,7 +480,8 @@ WRITE8_MEMBER(galaxian_state::galaxian_videoram_w)
 {
 	UINT8 *videoram = m_videoram;
 	/* update any video up to the current scanline */
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
 
 	/* store the data and mark the corresponding tile dirty */
 	videoram[offset] = data;
@@ -491,7 +492,8 @@ WRITE8_MEMBER(galaxian_state::galaxian_videoram_w)
 WRITE8_MEMBER(galaxian_state::galaxian_objram_w)
 {
 	/* update any video up to the current scanline */
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
 
 	/* store the data */
 	m_spriteram[offset] = data;
@@ -641,7 +643,8 @@ WRITE8_MEMBER(galaxian_state::galaxian_flip_screen_x_w)
 {
 	if (m_flipscreen_x != (data & 0x01))
 	{
-		m_screen->update_now();
+//		m_screen->update_now();
+		m_screen->update_partial(m_screen->vpos());
 
 		/* when the direction changes, we count a different number of clocks */
 		/* per frame, so we need to reset the origin of the stars to the current */
@@ -657,7 +660,9 @@ WRITE8_MEMBER(galaxian_state::galaxian_flip_screen_y_w)
 {
 	if (m_flipscreen_y != (data & 0x01))
 	{
-		m_screen->update_now();
+//		m_screen->update_now();
+		m_screen->update_partial(m_screen->vpos());
+
 		m_flipscreen_y = data & 0x01;
 		m_bg_tilemap->set_flip((m_flipscreen_x ? TILEMAP_FLIPX : 0) | (m_flipscreen_y ? TILEMAP_FLIPY : 0));
 	}
@@ -680,7 +685,10 @@ WRITE8_MEMBER(galaxian_state::galaxian_flip_screen_xy_w)
 WRITE8_MEMBER(galaxian_state::galaxian_stars_enable_w)
 {
 	if ((m_stars_enabled ^ data) & 0x01)
-		m_screen->update_now();
+	{
+//		m_screen->update_now();
+		m_screen->update_partial(m_screen->vpos());
+	}
 
 	if (!m_stars_enabled && (data & 0x01))
 	{
@@ -697,7 +705,10 @@ WRITE8_MEMBER(galaxian_state::galaxian_stars_enable_w)
 WRITE8_MEMBER(galaxian_state::scramble_background_enable_w)
 {
 	if ((m_background_enable ^ data) & 0x01)
-		m_screen->update_now();
+	{
+	//	m_screen->update_now();
+		m_screen->update_partial(m_screen->vpos());
+	}
 
 	m_background_enable = data & 0x01;
 }
@@ -706,7 +717,10 @@ WRITE8_MEMBER(galaxian_state::scramble_background_enable_w)
 WRITE8_MEMBER(galaxian_state::scramble_background_red_w)
 {
 	if ((m_background_red ^ data) & 0x01)
-		m_screen->update_now();
+	{
+	//	m_screen->update_now();
+		m_screen->update_partial(m_screen->vpos());
+	}
 
 	m_background_red = data & 0x01;
 }
@@ -715,7 +729,10 @@ WRITE8_MEMBER(galaxian_state::scramble_background_red_w)
 WRITE8_MEMBER(galaxian_state::scramble_background_green_w)
 {
 	if ((m_background_green ^ data) & 0x01)
-		m_screen->update_now();
+	{
+	//	m_screen->update_now();
+		m_screen->update_partial(m_screen->vpos());
+	}
 
 	m_background_green = data & 0x01;
 }
@@ -724,7 +741,10 @@ WRITE8_MEMBER(galaxian_state::scramble_background_green_w)
 WRITE8_MEMBER(galaxian_state::scramble_background_blue_w)
 {
 	if ((m_background_blue ^ data) & 0x01)
-		m_screen->update_now();
+	{
+	//	m_screen->update_now();
+		m_screen->update_partial(m_screen->vpos());
+	}
 
 	m_background_blue = data & 0x01;
 }
@@ -741,7 +761,8 @@ WRITE8_MEMBER(galaxian_state::galaxian_gfxbank_w)
 {
 	if (m_gfxbank[offset] != data)
 	{
-		m_screen->update_now();
+		//m_screen->update_now();
+		m_screen->update_partial(m_screen->vpos());
 		m_gfxbank[offset] = data;
 		m_bg_tilemap->mark_all_dirty();
 	}
diff --git a/src/mame/video/gyruss.c b/src/mame/video/gyruss.c
index 316a748a971..bf1038ac72b 100644
--- a/src/mame/video/gyruss.c
+++ b/src/mame/video/gyruss.c
@@ -93,7 +93,8 @@ PALETTE_INIT_MEMBER(gyruss_state, gyruss)
 
 WRITE8_MEMBER(gyruss_state::gyruss_spriteram_w)
 {
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
 	m_spriteram[offset] = data;
 }
 
diff --git a/src/mame/video/itech8.c b/src/mame/video/itech8.c
index 42a80eb9291..8920c8c423f 100644
--- a/src/mame/video/itech8.c
+++ b/src/mame/video/itech8.c
@@ -537,7 +537,8 @@ WRITE8_MEMBER(itech8_state::grmatch_palette_w)
 WRITE8_MEMBER(itech8_state::grmatch_xscroll_w)
 {
 	/* update the X scroll value */
-	m_screen->update_now();
+	//m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
 	m_grmatch_xscroll = data;
 }
 
diff --git a/src/mame/video/meadows.c b/src/mame/video/meadows.c
index 45d2cedfd3a..d378f15a7cf 100644
--- a/src/mame/video/meadows.c
+++ b/src/mame/video/meadows.c
@@ -64,7 +64,8 @@ WRITE8_MEMBER(meadows_state::meadows_videoram_w)
 
 WRITE8_MEMBER(meadows_state::meadows_spriteram_w)
 {
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
 	m_spriteram[offset] = data;
 }
 
diff --git a/src/mame/video/qix.c b/src/mame/video/qix.c
index 53cacf4a472..5bd717ecbc3 100644
--- a/src/mame/video/qix.c
+++ b/src/mame/video/qix.c
@@ -99,7 +99,8 @@ WRITE8_MEMBER(qix_state::qix_videoram_w)
 {
 	/* update the screen in case the game is writing "behind" the beam -
 	   Zookeeper likes to do this */
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
 
 	/* add in the upper bit of the address latch */
 	offset += (m_videoram_address[0] & 0x80) << 8;
@@ -113,7 +114,8 @@ WRITE8_MEMBER(qix_state::slither_videoram_w)
 {
 	/* update the screen in case the game is writing "behind" the beam -
 	   Zookeeper likes to do this */
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
 
 	/* add in the upper bit of the address latch */
 	offset += (m_videoram_address[0] & 0x80) << 8;
@@ -150,7 +152,8 @@ READ8_MEMBER(qix_state::qix_addresslatch_r)
 WRITE8_MEMBER(qix_state::qix_addresslatch_w)
 {
 	/* update the screen in case the game is writing "behind" the beam */
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
 
 	/* compute the value at the address latch */
 	offset = (m_videoram_address[0] << 8) | m_videoram_address[1];
@@ -163,7 +166,8 @@ WRITE8_MEMBER(qix_state::qix_addresslatch_w)
 WRITE8_MEMBER(qix_state::slither_addresslatch_w)
 {
 	/* update the screen in case the game is writing "behind" the beam */
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
 
 	/* compute the value at the address latch */
 	offset = (m_videoram_address[0] << 8) | m_videoram_address[1];
@@ -191,7 +195,10 @@ WRITE8_MEMBER(qix_state::qix_paletteram_w)
 	/* trigger an update if a currently visible pen has changed */
 	if (((offset >> 8) == m_palette_bank) &&
 		(old_data != data))
-		m_screen->update_now();
+	{
+	//	m_screen->update_now();
+		m_screen->update_partial(m_screen->vpos());
+	}
 
 	set_pen(offset);
 }
@@ -202,7 +209,8 @@ WRITE8_MEMBER(qix_state::qix_palettebank_w)
 	/* set the bank value */
 	if (m_palette_bank != (data & 3))
 	{
-		m_screen->update_now();
+		//m_screen->update_now();
+		m_screen->update_partial(m_screen->vpos());
 		m_palette_bank = data & 3;
 	}
 
diff --git a/src/mame/video/spacefb.c b/src/mame/video/spacefb.c
index c663655dc32..94499a825c3 100644
--- a/src/mame/video/spacefb.c
+++ b/src/mame/video/spacefb.c
@@ -19,14 +19,16 @@
 
 WRITE8_MEMBER(spacefb_state::port_0_w)
 {
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
 	m_port_0 = data;
 }
 
 
 WRITE8_MEMBER(spacefb_state::port_2_w)
 {
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
 	m_port_2 = data;
 }
 
diff --git a/src/mame/video/tp84.c b/src/mame/video/tp84.c
index fc2f2196bba..cf95dafbc4f 100644
--- a/src/mame/video/tp84.c
+++ b/src/mame/video/tp84.c
@@ -106,7 +106,8 @@ PALETTE_INIT_MEMBER(tp84_state, tp84)
 WRITE8_MEMBER(tp84_state::tp84_spriteram_w)
 {
 	/* the game multiplexes the sprites, so update now */
-	m_screen->update_now();
+//	m_screen->update_now();
+	m_screen->update_partial(m_screen->vpos());
 	m_spriteram[offset] = data;
 }