diff --git a/src/mame/namco/namcos1_v.cpp b/src/mame/namco/namcos1_v.cpp
index 72e9cd5afd6..b8ce4399293 100644
--- a/src/mame/namco/namcos1_v.cpp
+++ b/src/mame/namco/namcos1_v.cpp
@@ -68,15 +68,15 @@ void namcos1_state::TilemapCB(u16 code, int &tile, int &mask)
 
 void namcos1_state::video_start()
 {
-	/* set table for sprite color == 0x7f */
+	// set table for sprite color == 0x7f
 	for (int i = 0; i < 15; i++)
 		m_drawmode_table[i] = DRAWMODE_SHADOW;
 	m_drawmode_table[15] = DRAWMODE_NONE;
 
-	/* all palette entries are not affected by shadow sprites... */
+	// all palette entries are not affected by shadow sprites...
 	for (int i = 0; i < 0x2000; i++)
 		m_c116->shadow_table()[i] = i;
-	/* ... except for tilemap colors */
+	// ... except for tilemap colors
 	for (int i = 0x0800; i < 0x1000; i++)
 		m_c116->shadow_table()[i] = i + 0x0800;
 
@@ -95,11 +95,11 @@ void namcos1_state::video_start()
 
 void namcos1_state::spriteram_w(offs_t offset, u8 data)
 {
-	/* 0000-07ff work ram */
-	/* 0800-0fff sprite ram */
+	// 0000-07ff work ram
+	// 0800-0fff sprite ram
 	m_spriteram[offset] = data;
 
-	/* a write to this offset tells the sprite chip to buffer the sprite list */
+	// a write to this offset tells the sprite chip to buffer the sprite list
 	if (offset == 0x0ff2)
 		m_copy_sprites = true;
 }
@@ -135,7 +135,7 @@ sprite format:
 void namcos1_state::draw_sprites(screen_device &screen, bitmap_ind16 &bitmap, const rectangle &cliprect)
 {
 	u8 *spriteram = m_spriteram + 0x800;
-	const u8 *source = &spriteram[0x800-0x20];   /* the last is NOT a sprite */
+	const u8 *source = &spriteram[0x800-0x20]; // the last is NOT a sprite
 	const u8 *finish = &spriteram[0];
 	gfx_element *gfx = m_gfxdecode->gfx(0);
 
@@ -175,7 +175,7 @@ void namcos1_state::draw_sprites(screen_device &screen, bitmap_ind16 &bitmap, co
 			flipy = !flipy;
 		}
 
-		sy++;   /* sprites are buffered and delayed by one scanline */
+		sy++; // sprites are buffered and delayed by one scanline
 
 		gfx->set_source_clip(tx, sizex, ty, sizey);
 		if (color != 0x7f)
@@ -207,13 +207,13 @@ u32 namcos1_state::screen_update(screen_device &screen, bitmap_ind16 &bitmap, co
 {
 	rectangle new_clip = cliprect;
 
-	/* flip screen is embedded in the sprite control registers */
+	// flip screen is embedded in the sprite control registers
 	flip_screen_set(m_spriteram[0x0ff6] & 1);
 
-	/* background color */
+	// background color
 	bitmap.fill(m_c116->black_pen(), cliprect);
 
-	/* berabohm uses asymmetrical visibility windows to iris on the character */
+	// berabohm uses asymmetrical visibility windows to iris on the character
 	int i = m_c116->get_reg(0) - 1;                     // min x
 	if (new_clip.min_x < i) new_clip.min_x = i;
 	i = m_c116->get_reg(1) - 1 - 1;                     // max x
@@ -230,8 +230,8 @@ u32 namcos1_state::screen_update(screen_device &screen, bitmap_ind16 &bitmap, co
 
 	screen.priority().fill(0, new_clip);
 
-	/* bit 0-2 priority */
-	/* bit 3   disable  */
+	// bit 0-2 priority
+	// bit 3   disable
 	for (int priority = 0; priority < 8; priority++)
 	{
 		m_c123tmap->draw(screen, bitmap, new_clip, priority, priority, 0);
@@ -244,9 +244,9 @@ u32 namcos1_state::screen_update(screen_device &screen, bitmap_ind16 &bitmap, co
 
 void namcos1_state::screen_vblank(int state)
 {
-	// rising edge
 	if (state)
 	{
+		// rising edge
 		if (m_copy_sprites)
 		{
 			u8 *spriteram = m_spriteram + 0x800;
@@ -265,6 +265,8 @@ void namcos1_state::screen_vblank(int state)
 	}
 	else
 	{
+		// falling edge
+		// splatter 2nd bossfight music fails if audiocpu irq is at the same time as main/sub irq
 		m_audiocpu->set_input_line(M6809_IRQ_LINE, ASSERT_LINE);
 		m_mcu->set_input_line(HD6301_IRQ1_LINE, ASSERT_LINE);
 	}
diff --git a/src/mame/orca/espial.cpp b/src/mame/orca/espial.cpp
index 1432286213b..500efa83f76 100644
--- a/src/mame/orca/espial.cpp
+++ b/src/mame/orca/espial.cpp
@@ -3,7 +3,10 @@
 
 /***************************************************************************
 
- Espial hardware games
+Espial hardware games
+
+2 XTALS (12.0MHz and 18.432MHz), both CPUs are 3.0MHz and the AY is 1.5MHz.
+18.432MHz XTAL is probably for the pixel clock.
 
 Espial: The Orca logo is displayed, but looks to be "blacked out" via the
         color PROMs by having 0x1c & 0x1d set to black.
@@ -43,7 +46,6 @@ Stephh's notes (based on the games Z80 code and some tests) :
 
 #include "cpu/z80/z80.h"
 #include "machine/gen_latch.h"
-#include "machine/timer.h"
 #include "machine/watchdog.h"
 #include "sound/ay8910.h"
 
@@ -67,9 +69,11 @@ public:
 		m_colorram(*this, "colorram"),
 		m_maincpu(*this, "maincpu"),
 		m_audiocpu(*this, "audiocpu"),
+		m_screen(*this, "screen"),
 		m_gfxdecode(*this, "gfxdecode"),
 		m_palette(*this, "palette"),
-		m_soundlatch(*this, "soundlatch")
+		m_soundlatch(*this, "soundlatch%u", 0),
+		m_aysnd(*this, "aysnd")
 	{ }
 
 	void espial(machine_config &config);
@@ -88,22 +92,29 @@ protected:
 
 	// video-related
 	tilemap_t *m_bg_tilemap = nullptr;
-	uint8_t m_flipscreen = 0U;
+	uint8_t m_flipscreen = 0;
 
 	// sound-related
-	uint8_t m_main_nmi_enabled = 0U;
-	uint8_t m_sound_nmi_enabled = 0U;
+	uint8_t m_main_nmi_enabled = 0;
+	uint8_t m_sound_nmi_enabled = 0;
+	uint8_t m_sound_nmi_freq = 0;
+	emu_timer *sound_nmi_timer;
 
 	// devices
 	required_device<cpu_device> m_maincpu;
 	required_device<cpu_device> m_audiocpu;
+	required_device<screen_device> m_screen;
 	required_device<gfxdecode_device> m_gfxdecode;
 	required_device<palette_device> m_palette;
-	required_device<generic_latch_8_device> m_soundlatch;
+	required_device_array<generic_latch_8_device, 2> m_soundlatch;
+	required_device<ay8910_device> m_aysnd;
 
 	void master_interrupt_mask_w(uint8_t data);
-	void master_soundlatch_w(uint8_t data);
 	void sound_nmi_mask_w(uint8_t data);
+	void porta_w(offs_t offset, uint8_t data, uint8_t mem_mask);
+	TIMER_CALLBACK_MEMBER(sound_nmi_gen);
+	void vblank(int state);
+
 	void videoram_w(offs_t offset, uint8_t data);
 	void colorram_w(offs_t offset, uint8_t data);
 	void attributeram_w(offs_t offset, uint8_t data);
@@ -112,9 +123,8 @@ protected:
 	TILE_GET_INFO_MEMBER(get_tile_info);
 	void palette(palette_device &palette) const;
 	uint32_t screen_update(screen_device &screen, bitmap_ind16 &bitmap, const rectangle &cliprect);
-	INTERRUPT_GEN_MEMBER(sound_nmi_gen);
-	TIMER_DEVICE_CALLBACK_MEMBER(scanline);
 	void draw_sprites(bitmap_ind16 &bitmap, const rectangle &cliprect);
+
 	void main_map(address_map &map) ATTR_COLD;
 	void sound_io_map(address_map &map) ATTR_COLD;
 	void sound_map(address_map &map) ATTR_COLD;
@@ -123,7 +133,9 @@ protected:
 class netwars_state : public espial_state
 {
 public:
-	using espial_state::espial_state;
+	netwars_state(const machine_config &mconfig, device_type type, const char *tag) :
+		espial_state(mconfig, type, tag)
+	{ }
 
 	void netwars(machine_config &config);
 
@@ -135,7 +147,32 @@ private:
 };
 
 
-/***************************************************************************
+
+/*************************************
+ *
+ *  Machine initialization
+ *
+ *************************************/
+
+void espial_state::machine_start()
+{
+	save_item(NAME(m_flipscreen));
+	save_item(NAME(m_main_nmi_enabled));
+	save_item(NAME(m_sound_nmi_enabled));
+	save_item(NAME(m_sound_nmi_freq));
+
+	sound_nmi_timer = timer_alloc(FUNC(espial_state::sound_nmi_gen), this);
+}
+
+void espial_state::machine_reset()
+{
+	m_main_nmi_enabled = false;
+	m_sound_nmi_enabled = false;
+}
+
+
+
+/*************************************
 
   Convert the color PROMs into a more useable format.
 
@@ -153,7 +190,7 @@ private:
         -- 470 ohm resistor  -- RED
   bit 0 -- 1  kohm resistor  -- RED
 
-***************************************************************************/
+*************************************/
 
 void espial_state::palette(palette_device &palette) const
 {
@@ -168,11 +205,13 @@ void espial_state::palette(palette_device &palette) const
 		bit1 = BIT(color_prom[i], 1);
 		bit2 = BIT(color_prom[i], 2);
 		int const r = 0x21 * bit0 + 0x47 * bit1 + 0x97 * bit2;
+
 		// green component
 		bit0 = BIT(color_prom[i], 3);
 		bit1 = BIT(color_prom[i + palette.entries()], 0);
 		bit2 = BIT(color_prom[i + palette.entries()], 1);
 		int const g = 0x21 * bit0 + 0x47 * bit1 + 0x97 * bit2;
+
 		// blue component
 		bit0 = 0;
 		bit1 = BIT(color_prom[i + palette.entries()], 2);
@@ -185,23 +224,6 @@ void espial_state::palette(palette_device &palette) const
 
 
 
-/***************************************************************************
-
-  Callbacks for the TileMap code
-
-***************************************************************************/
-
-TILE_GET_INFO_MEMBER(espial_state::get_tile_info)
-{
-	uint8_t const code = m_videoram[tile_index];
-	uint8_t const col = m_colorram[tile_index];
-	uint8_t const attr = m_attributeram[tile_index];
-
-	tileinfo.set(0, code | ((attr & 0x03) << 8), col & 0x3f, TILE_FLIPYX(attr >> 2));
-}
-
-
-
 /*************************************
  *
  *  Video system start
@@ -212,61 +234,25 @@ void espial_state::video_start()
 {
 	m_bg_tilemap = &machine().tilemap().create(*m_gfxdecode, tilemap_get_info_delegate(*this, FUNC(espial_state::get_tile_info)), TILEMAP_SCAN_ROWS, 8, 8, 32, 32);
 	m_bg_tilemap->set_scroll_cols(32);
-
-	save_item(NAME(m_flipscreen));
 }
 
 void netwars_state::video_start()
 {
 	// Net Wars has a tile map that's twice as big as Espial's
 	m_bg_tilemap = &machine().tilemap().create(*m_gfxdecode, tilemap_get_info_delegate(*this, FUNC(netwars_state::get_tile_info)), TILEMAP_SCAN_ROWS, 8, 8, 32, 64);
-
 	m_bg_tilemap->set_scroll_cols(32);
-
-	save_item(NAME(m_flipscreen));
 }
 
-
-/*************************************
- *
- *  Memory handlers
- *
- *************************************/
-
-void espial_state::videoram_w(offs_t offset, uint8_t data)
+TILE_GET_INFO_MEMBER(espial_state::get_tile_info)
 {
-	m_videoram[offset] = data;
-	m_bg_tilemap->mark_tile_dirty(offset);
+	uint8_t const code = m_videoram[tile_index];
+	uint8_t const col = m_colorram[tile_index];
+	uint8_t const attr = m_attributeram[tile_index];
+
+	tileinfo.set(0, code | ((attr & 0x03) << 8), col & 0x3f, TILE_FLIPYX(attr >> 2));
 }
 
 
-void espial_state::colorram_w(offs_t offset, uint8_t data)
-{
-	m_colorram[offset] = data;
-	m_bg_tilemap->mark_tile_dirty(offset);
-}
-
-
-void espial_state::attributeram_w(offs_t offset, uint8_t data)
-{
-	m_attributeram[offset] = data;
-	m_bg_tilemap->mark_tile_dirty(offset);
-}
-
-
-void espial_state::scrollram_w(offs_t offset, uint8_t data)
-{
-	m_scrollram[offset] = data;
-	m_bg_tilemap->set_scrolly(offset, data);
-}
-
-
-void espial_state::flipscreen_w(uint8_t data)
-{
-	m_flipscreen = data;
-	m_bg_tilemap->set_flip(m_flipscreen ? TILEMAP_FLIPX | TILEMAP_FLIPY : 0);
-}
-
 
 /*************************************
  *
@@ -333,7 +319,6 @@ void espial_state::draw_sprites(bitmap_ind16 &bitmap, const rectangle &cliprect)
 	}
 }
 
-
 uint32_t espial_state::screen_update(screen_device &screen, bitmap_ind16 &bitmap, const rectangle &cliprect)
 {
 	m_bg_tilemap->draw(screen, bitmap, cliprect, 0, 0);
@@ -342,20 +327,66 @@ uint32_t espial_state::screen_update(screen_device &screen, bitmap_ind16 &bitmap
 }
 
 
-void espial_state::machine_reset()
-{
-	m_flipscreen = 0;
 
-	m_main_nmi_enabled = false;
-	m_sound_nmi_enabled = false;
+/*************************************
+ *
+ *  Memory handlers
+ *
+ *************************************/
+
+void espial_state::vblank(int state)
+{
+	// vblank irq
+	if (state && m_main_nmi_enabled)
+		m_maincpu->pulse_input_line(INPUT_LINE_NMI, attotime::zero);
+
+	// timer irq, checks soundlatch port then updates some sound related work RAM buffers
+	if (state)
+		m_maincpu->set_input_line(0, HOLD_LINE);
 }
 
-void espial_state::machine_start()
+
+TIMER_CALLBACK_MEMBER(espial_state::sound_nmi_gen)
 {
-	save_item(NAME(m_sound_nmi_enabled));
+	if (m_sound_nmi_enabled)
+		m_audiocpu->pulse_input_line(INPUT_LINE_NMI, attotime::zero);
 }
 
 
+void espial_state::videoram_w(offs_t offset, uint8_t data)
+{
+	m_videoram[offset] = data;
+	m_bg_tilemap->mark_tile_dirty(offset);
+}
+
+
+void espial_state::colorram_w(offs_t offset, uint8_t data)
+{
+	m_colorram[offset] = data;
+	m_bg_tilemap->mark_tile_dirty(offset);
+}
+
+
+void espial_state::attributeram_w(offs_t offset, uint8_t data)
+{
+	m_attributeram[offset] = data;
+	m_bg_tilemap->mark_tile_dirty(offset);
+}
+
+
+void espial_state::scrollram_w(offs_t offset, uint8_t data)
+{
+	m_scrollram[offset] = data;
+	m_bg_tilemap->set_scrolly(offset, data);
+}
+
+
+void espial_state::flipscreen_w(uint8_t data)
+{
+	m_flipscreen = data;
+	m_bg_tilemap->set_flip(m_flipscreen ? TILEMAP_FLIPX | TILEMAP_FLIPY : 0);
+}
+
 void espial_state::master_interrupt_mask_w(uint8_t data)
 {
 	m_main_nmi_enabled = ~(data & 1);
@@ -367,31 +398,46 @@ void espial_state::sound_nmi_mask_w(uint8_t data)
 	m_sound_nmi_enabled = data & 1;
 }
 
-TIMER_DEVICE_CALLBACK_MEMBER(espial_state::scanline)
+void espial_state::porta_w(offs_t offset, uint8_t data, uint8_t mem_mask)
 {
-	int const scanline = param;
+	if (mem_mask && data != m_sound_nmi_freq)
+	{
+		// sound NMI frequency
+		m_sound_nmi_freq = data;
+		attotime period;
 
-	if (scanline == 240 && m_main_nmi_enabled) // vblank-out irq
-		m_maincpu->pulse_input_line(INPUT_LINE_NMI, attotime::zero);
+		// netwars writes 0xf8 and expects 32 NMIs per frame
+		// espial writes 0xfe and expects 4 NMIs per frame
+		switch (data)
+		{
+			case 0:
+				period = attotime::never;
+				break;
 
-	if (scanline == 16) // timer irq, checks soundlatch port then updates some sound related work RAM buffers
-		m_maincpu->set_input_line(0, HOLD_LINE);
+			case 0xfe:
+				period = m_screen->frame_period() / 4;
+				break;
+
+			case 0xf8:
+				period = m_screen->frame_period() / 32;
+				break;
+
+			default:
+				logerror("%s: unknown sound NMI frequency %02X", machine().describe_context(), data);
+				return;
+		}
+
+		sound_nmi_timer->adjust(period, 0, period);
+	}
 }
 
 
-INTERRUPT_GEN_MEMBER(espial_state::sound_nmi_gen)
-{
-	if (m_sound_nmi_enabled)
-		m_audiocpu->pulse_input_line(INPUT_LINE_NMI, attotime::zero);
-}
-
-
-void espial_state::master_soundlatch_w(uint8_t data)
-{
-	m_soundlatch->write(data);
-	m_audiocpu->set_input_line(0, HOLD_LINE);
-}
 
+/*************************************
+ *
+ *  Address maps
+ *
+ *************************************/
 
 void espial_state::main_map(address_map &map)
 {
@@ -401,7 +447,7 @@ void espial_state::main_map(address_map &map)
 	map(0x6082, 0x6082).portr("DSW1");
 	map(0x6083, 0x6083).portr("IN1");
 	map(0x6084, 0x6084).portr("IN2");
-	map(0x6090, 0x6090).r("soundlatch2", FUNC(generic_latch_8_device::read)).w(FUNC(espial_state::master_soundlatch_w));
+	map(0x6090, 0x6090).r(m_soundlatch[1], FUNC(generic_latch_8_device::read)).w(m_soundlatch[0], FUNC(generic_latch_8_device::write));
 	map(0x7000, 0x7000).rw("watchdog", FUNC(watchdog_timer_device::reset_r), FUNC(watchdog_timer_device::reset_w));
 	map(0x7100, 0x7100).w(FUNC(espial_state::master_interrupt_mask_w));
 	map(0x7200, 0x7200).w(FUNC(espial_state::flipscreen_w));
@@ -427,7 +473,7 @@ void netwars_state::main_map(address_map &map)
 	map(0x6082, 0x6082).portr("DSW1");
 	map(0x6083, 0x6083).portr("IN1");
 	map(0x6084, 0x6084).portr("IN2");
-	map(0x6090, 0x6090).r("soundlatch2", FUNC(generic_latch_8_device::read)).w(FUNC(netwars_state::master_soundlatch_w));
+	map(0x6090, 0x6090).r(m_soundlatch[1], FUNC(generic_latch_8_device::read)).w(m_soundlatch[0], FUNC(generic_latch_8_device::write));
 	map(0x7000, 0x7000).rw("watchdog", FUNC(watchdog_timer_device::reset_r), FUNC(watchdog_timer_device::reset_w));
 	map(0x7100, 0x7100).w(FUNC(netwars_state::master_interrupt_mask_w));
 	map(0x7200, 0x7200).w(FUNC(netwars_state::flipscreen_w));
@@ -446,16 +492,23 @@ void espial_state::sound_map(address_map &map)
 	map(0x0000, 0x1fff).rom();
 	map(0x2000, 0x23ff).ram();
 	map(0x4000, 0x4000).w(FUNC(espial_state::sound_nmi_mask_w));
-	map(0x6000, 0x6000).r(m_soundlatch, FUNC(generic_latch_8_device::read)).w("soundlatch2", FUNC(generic_latch_8_device::write));
+	map(0x6000, 0x6000).r(m_soundlatch[0], FUNC(generic_latch_8_device::read)).w(m_soundlatch[1], FUNC(generic_latch_8_device::write));
 }
 
 void espial_state::sound_io_map(address_map &map)
 {
 	map.global_mask(0xff);
-	map(0x00, 0x01).w("aysnd", FUNC(ay8910_device::address_data_w));
+	map(0x00, 0x01).w(m_aysnd, FUNC(ay8910_device::address_data_w));
 }
 
 
+
+/*************************************
+ *
+ *  Input ports
+ *
+ *************************************/
+
 // verified from Z80 code
 static INPUT_PORTS_START( espial )
 	PORT_START("IN0")
@@ -580,6 +633,13 @@ static INPUT_PORTS_START( netwars )
 INPUT_PORTS_END
 
 
+
+/*************************************
+ *
+ *  GFX layouts
+ *
+ *************************************/
+
 static const gfx_layout charlayout =
 {
 	8,8,
@@ -610,29 +670,35 @@ GFXDECODE_END
 
 
 
+/*************************************
+ *
+ *  Machine configs
+ *
+ *************************************/
 
 void espial_state::espial(machine_config &config)
 {
 	// basic machine hardware
-	Z80(config, m_maincpu, 3'072'000);   // 3.072 MHz
+	Z80(config, m_maincpu, 12_MHz_XTAL / 4);
 	m_maincpu->set_addrmap(AS_PROGRAM, &espial_state::main_map);
-	TIMER(config, "scantimer").configure_scanline(FUNC(espial_state::scanline), "screen", 0, 1);
 
-	Z80(config, m_audiocpu, 3'072'000);  // 2 MHz??????
+	Z80(config, m_audiocpu, 12_MHz_XTAL / 4);
 	m_audiocpu->set_addrmap(AS_PROGRAM, &espial_state::sound_map);
 	m_audiocpu->set_addrmap(AS_IO, &espial_state::sound_io_map);
-	m_audiocpu->set_periodic_int(FUNC(espial_state::sound_nmi_gen), attotime::from_hz(4 * 60));
+
+	config.set_maximum_quantum(attotime::from_hz(600));
 
 	WATCHDOG_TIMER(config, "watchdog");
 
 	// video hardware
-	screen_device &screen(SCREEN(config, "screen", SCREEN_TYPE_RASTER));
-	screen.set_refresh_hz(60);
-	screen.set_vblank_time(ATTOSECONDS_IN_USEC(2500)); // not accurate
-	screen.set_size(32*8, 32*8);
-	screen.set_visarea(0*8, 32*8-1, 2*8, 30*8-1);
-	screen.set_screen_update(FUNC(espial_state::screen_update));
-	screen.set_palette(m_palette);
+	SCREEN(config, m_screen, SCREEN_TYPE_RASTER);
+	m_screen->set_refresh_hz(59);
+	m_screen->set_vblank_time(ATTOSECONDS_IN_USEC(2500)); // not accurate
+	m_screen->set_size(32*8, 32*8);
+	m_screen->set_visarea(0*8, 32*8-1, 2*8, 30*8-1);
+	m_screen->set_screen_update(FUNC(espial_state::screen_update));
+	m_screen->set_palette(m_palette);
+	m_screen->screen_vblank().set(FUNC(espial_state::vblank));
 
 	GFXDECODE(config, m_gfxdecode, m_palette, gfx_espial);
 	PALETTE(config, m_palette, FUNC(espial_state::palette), 256);
@@ -640,10 +706,14 @@ void espial_state::espial(machine_config &config)
 	// sound hardware
 	SPEAKER(config, "mono").front_center();
 
-	GENERIC_LATCH_8(config, m_soundlatch);
-	GENERIC_LATCH_8(config, "soundlatch2");
+	GENERIC_LATCH_8(config, m_soundlatch[0]);
+	m_soundlatch[0]->data_pending_callback().set_inputline(m_audiocpu, 0);
 
-	AY8910(config, "aysnd", 1'500'000).add_route(ALL_OUTPUTS, "mono", 0.50);
+	GENERIC_LATCH_8(config, m_soundlatch[1]);
+
+	AY8910(config, m_aysnd, 12_MHz_XTAL / 8).add_route(ALL_OUTPUTS, "mono", 0.50);
+	m_aysnd->port_a_write_callback().set(FUNC(espial_state::porta_w));
+	m_aysnd->port_b_write_callback().set_nop(); // spams 0x00
 }
 
 void netwars_state::netwars(machine_config &config)
@@ -652,18 +722,15 @@ void netwars_state::netwars(machine_config &config)
 
 	// basic machine hardware
 	m_maincpu->set_addrmap(AS_PROGRAM, &netwars_state::main_map);
-
-	// video hardware
-	subdevice<screen_device>("screen")->set_size(32*8, 64*8);
 }
 
 
 
-/***************************************************************************
-
-  Game driver(s)
-
-***************************************************************************/
+/*************************************
+ *
+ *  ROM definitions
+ *
+ *************************************/
 
 ROM_START( espial )
 	ROM_REGION( 0x10000, "maincpu", 0 )
@@ -786,6 +853,13 @@ ROM_END
 } // anonymous namespace
 
 
+
+/*************************************
+ *
+ *  Game driver(s)
+ *
+ *************************************/
+
 GAME( 1983, espial,  0,      espial,  espial,  espial_state,  empty_init, ROT0,  "Orca / Thunderbolt",             "Espial (Europe)",                MACHINE_SUPPORTS_SAVE )
 GAME( 1983, espialj, espial, espial,  espial,  espial_state,  empty_init, ROT0,  "Orca / Thunderbolt",             "Espial (Japan)",                 MACHINE_SUPPORTS_SAVE )
 GAME( 1983, espialn, espial, espial,  espial,  espial_state,  empty_init, ROT0,  "Orca / Thunderbolt",             "Espial (Nova Apparate license)", MACHINE_SUPPORTS_SAVE )
diff --git a/src/mame/orca/orca40c.cpp b/src/mame/orca/orca40c.cpp
index bd5ebac0b26..d694ae68524 100644
--- a/src/mame/orca/orca40c.cpp
+++ b/src/mame/orca/orca40c.cpp
@@ -28,17 +28,17 @@
 
 DEFINE_DEVICE_TYPE(ORCA_OVG_40C, orca_ovg_40c_device, "orca_ovg_40c", "Orca OVG 40c video PCB")
 
-orca_ovg_40c_device::orca_ovg_40c_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
-	: device_t(mconfig, ORCA_OVG_40C, tag, owner, clock),
-		device_gfx_interface(mconfig, *this, nullptr, "palette"),
-		device_video_interface(mconfig, *this),
-		m_videoram(*this, "videoram"),
-		m_videoram_2(*this,"videoram_2"),
-		m_attributeram(*this, "attributeram"),
-		m_spriteram(*this, "spriteram"),
-		m_bulletsram(*this, "bulletsram"),
-		m_percuss_hardware(false),
-		m_flip_screen(false)
+orca_ovg_40c_device::orca_ovg_40c_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) :
+	device_t(mconfig, ORCA_OVG_40C, tag, owner, clock),
+	device_gfx_interface(mconfig, *this, nullptr, "palette"),
+	device_video_interface(mconfig, *this),
+	m_videoram(*this, "videoram"),
+	m_videoram_2(*this,"videoram_2"),
+	m_attributeram(*this, "attributeram"),
+	m_spriteram(*this, "spriteram"),
+	m_bulletsram(*this, "bulletsram"),
+	m_percuss_hardware(false),
+	m_flip_screen(false)
 {
 }
 
diff --git a/src/mame/orca/vastar.cpp b/src/mame/orca/vastar.cpp
index 56b1e11bc7b..f3b679129f5 100644
--- a/src/mame/orca/vastar.cpp
+++ b/src/mame/orca/vastar.cpp
@@ -700,7 +700,7 @@ ROM_START( dogfightp ) // all 2732
 	ROM_LOAD( "10.7p",     0x1800, 0x1000, CRC(2cb51793) SHA1(d90177ef28730774202a04a0846281537a1883df) )
 
 	ROM_REGION( 0x0040, "videopcb:proms", 0 ) // on ORCA OVG-40c sub board
-	ROM_LOAD( "blue.2a.82s123", 0x0000, 0x0020, CRC(aa839a24) SHA1(9b8217e1c257d24e873888fd083c099fc93c7878) ) //doesn't match parent
+	ROM_LOAD( "blue.2a.82s123", 0x0000, 0x0020, CRC(aa839a24) SHA1(9b8217e1c257d24e873888fd083c099fc93c7878) ) // doesn't match parent
 	ROM_LOAD( "pink.2b.82s123", 0x0020, 0x0020, CRC(596ae457) SHA1(1c1a3130d88c5fd5c66ce9f91d97a09c0a0b535f) )
 ROM_END
 
diff --git a/src/mame/orca/zodiack.cpp b/src/mame/orca/zodiack.cpp
index 5620f974d64..5bdbdc55089 100644
--- a/src/mame/orca/zodiack.cpp
+++ b/src/mame/orca/zodiack.cpp
@@ -117,11 +117,12 @@ public:
 		driver_device(mconfig, type, tag),
 		m_maincpu(*this, "maincpu"),
 		m_audiocpu(*this, "audiocpu"),
-		m_soundlatch(*this, "soundlatch%u", 0)
+		m_screen(*this, "screen"),
+		m_soundlatch(*this, "soundlatch%u", 0),
+		m_aysnd(*this, "aysnd")
 	{ }
 
 	void zodiack(machine_config &config);
-	void dogfight(machine_config &config);
 	void percuss(machine_config &config);
 
 protected:
@@ -133,18 +134,23 @@ private:
 	void irq_mask_w(uint8_t data);
 	void sound_nmi_enable_w(uint8_t data);
 	void control_w(uint8_t data);
+	void porta_w(offs_t offset, uint8_t data, uint8_t mem_mask);
 
 	// devices
 	required_device<z80_device> m_maincpu;
 	required_device<z80_device> m_audiocpu;
+	required_device<screen_device> m_screen;
 	required_device_array<generic_latch_8_device, 2> m_soundlatch;
+	required_device<ay8910_device> m_aysnd;
 
 	// state
 	uint8_t m_main_nmi_enabled = 0;
 	uint8_t m_main_irq_enabled = 0;
 	uint8_t m_sound_nmi_enabled = 0;
+	uint8_t m_sound_nmi_freq = 0;
+	emu_timer *sound_nmi_timer;
 
-	INTERRUPT_GEN_MEMBER(sound_nmi_gen);
+	TIMER_CALLBACK_MEMBER(sound_nmi_gen);
 	void vblank(int state);
 
 	void io_map(address_map &map) ATTR_COLD;
@@ -152,6 +158,39 @@ private:
 	void sound_map(address_map &map) ATTR_COLD;
 };
 
+
+
+/*************************************
+ *
+ *  Machine initialization
+ *
+ *************************************/
+
+void zodiack_state::machine_start()
+{
+	save_item(NAME(m_main_nmi_enabled));
+	save_item(NAME(m_main_irq_enabled));
+	save_item(NAME(m_sound_nmi_enabled));
+	save_item(NAME(m_sound_nmi_freq));
+
+	sound_nmi_timer = timer_alloc(FUNC(zodiack_state::sound_nmi_gen), this);
+}
+
+void zodiack_state::machine_reset()
+{
+	m_main_nmi_enabled = 0;
+	m_main_irq_enabled = 0;
+	m_sound_nmi_enabled = 0;
+}
+
+
+
+/*************************************
+ *
+ *  Memory handlers
+ *
+ *************************************/
+
 void zodiack_state::nmi_mask_w(uint8_t data)
 {
 	m_main_nmi_enabled = (data & 1) ^ 1;
@@ -176,7 +215,7 @@ void zodiack_state::vblank(int state)
 		m_maincpu->set_input_line(0, HOLD_LINE);
 }
 
-INTERRUPT_GEN_MEMBER(zodiack_state::sound_nmi_gen)
+TIMER_CALLBACK_MEMBER(zodiack_state::sound_nmi_gen)
 {
 	if (m_sound_nmi_enabled)
 		m_audiocpu->pulse_input_line(INPUT_LINE_NMI, attotime::zero);
@@ -190,6 +229,46 @@ void zodiack_state::control_w(uint8_t data)
 	// Bit 2 - ????
 }
 
+void zodiack_state::porta_w(offs_t offset, uint8_t data, uint8_t mem_mask)
+{
+	if (mem_mask && data != m_sound_nmi_freq)
+	{
+		// sound NMI frequency
+		m_sound_nmi_freq = data;
+		attotime period;
+
+		// dogfight writes 0xc0 and expects 4 NMIs per frame
+		// others write 0xe0 and expect 8 NMIs per frame
+		switch (data)
+		{
+			case 0:
+				period = attotime::never;
+				break;
+
+			case 0xc0:
+				period = m_screen->frame_period() / 4;
+				break;
+
+			case 0xe0:
+				period = m_screen->frame_period() / 8;
+				break;
+
+			default:
+				logerror("%s: unknown sound NMI frequency %02X", machine().describe_context(), data);
+				return;
+		}
+
+		sound_nmi_timer->adjust(period, 0, period);
+	}
+}
+
+
+
+/*************************************
+ *
+ *  Address maps
+ *
+ *************************************/
 
 void zodiack_state::main_map(address_map &map)
 {
@@ -224,11 +303,17 @@ void zodiack_state::sound_map(address_map &map)
 void zodiack_state::io_map(address_map &map)
 {
 	map.global_mask(0xff);
-	map(0x00, 0x01).w("aysnd", FUNC(ay8910_device::address_data_w));
+	map(0x00, 0x01).w(m_aysnd, FUNC(ay8910_device::address_data_w));
 }
 
 
 
+/*************************************
+ *
+ *  Input ports
+ *
+ *************************************/
+
 static INPUT_PORTS_START( zodiack )
 	PORT_START("DSW0") // never read in this game
 	PORT_BIT( 0xff, IP_ACTIVE_HIGH, IPT_UNUSED )
@@ -540,39 +625,30 @@ static INPUT_PORTS_START( bounty )
 	PORT_BIT( 0x80, IP_ACTIVE_HIGH, IPT_JOYSTICK_LEFT ) PORT_8WAY
 INPUT_PORTS_END
 
-void zodiack_state::machine_start()
-{
-	save_item(NAME(m_main_nmi_enabled));
-	save_item(NAME(m_main_irq_enabled));
-	save_item(NAME(m_sound_nmi_enabled));
-}
-
-void zodiack_state::machine_reset()
-{
-	m_main_nmi_enabled = 0;
-	m_main_irq_enabled = 0;
-	m_sound_nmi_enabled = 0;
-}
 
 
+/*************************************
+ *
+ *  Machine configs
+ *
+ *************************************/
 
 void zodiack_state::zodiack(machine_config &config)
 {
 	// basic machine hardware
-	Z80(config, m_maincpu, XTAL(18'432'000) / 6);
+	Z80(config, m_maincpu, 18.432_MHz_XTAL / 6);
 	m_maincpu->set_addrmap(AS_PROGRAM, &zodiack_state::main_map);
 
-	Z80(config, m_audiocpu, XTAL(18'432'000) / 6);
+	Z80(config, m_audiocpu, 18.432_MHz_XTAL / 6);
 	m_audiocpu->set_addrmap(AS_PROGRAM, &zodiack_state::sound_map);
 	m_audiocpu->set_addrmap(AS_IO, &zodiack_state::io_map);
-	m_audiocpu->set_periodic_int(FUNC(zodiack_state::sound_nmi_gen), attotime::from_hz(8 * 60)); // sound tempo - unknown source, timing is guessed
 
 	config.set_maximum_quantum(attotime::from_hz(600));
 
 	WATCHDOG_TIMER(config, "watchdog");
 
 	// video hardware
-	SCREEN(config, "screen", SCREEN_TYPE_RASTER).screen_vblank().set(FUNC(zodiack_state::vblank));
+	SCREEN(config, m_screen, SCREEN_TYPE_RASTER).screen_vblank().set(FUNC(zodiack_state::vblank));
 
 	orca_ovg_40c_device &videopcb(ORCA_OVG_40C(config, "videopcb", 0));
 	videopcb.set_screen("screen");
@@ -585,7 +661,8 @@ void zodiack_state::zodiack(machine_config &config)
 
 	GENERIC_LATCH_8(config, m_soundlatch[1]);
 
-	AY8910(config, "aysnd", XTAL(18'432'000) / 12).add_route(ALL_OUTPUTS, "mono", 0.50);
+	AY8910(config, m_aysnd, 18.432_MHz_XTAL / 12).add_route(ALL_OUTPUTS, "mono", 0.50);
+	m_aysnd->port_a_write_callback().set(FUNC(zodiack_state::porta_w));
 }
 
 void zodiack_state::percuss(machine_config &config)
@@ -596,19 +673,13 @@ void zodiack_state::percuss(machine_config &config)
 	videopcb.set_percuss_hardware(true);
 }
 
-void zodiack_state::dogfight(machine_config &config)
-{
-	zodiack(config);
-
-	m_audiocpu->set_periodic_int(FUNC(zodiack_state::sound_nmi_gen), attotime::from_hz(4 * 60)); // 4 interrupts per frame
-}
 
 
-/***************************************************************************
-
-  Game driver(s)
-
-***************************************************************************/
+/*************************************
+ *
+ *  ROM definitions
+ *
+ *************************************/
 
 ROM_START( zodiack )
 	ROM_REGION( 0x10000, "maincpu", 0 )
@@ -735,9 +806,16 @@ ROM_END
 } // anonymous namespace
 
 
-GAME( 1983, zodiack,  0,      zodiack,  zodiack,  zodiack_state, empty_init, ROT270, "Orca (Esco Trading Co., Inc. license)", "Zodiack",                 MACHINE_IMPERFECT_COLORS | MACHINE_SUPPORTS_SAVE ) // bullet color needs to be verified
-GAME( 1983, dogfight, 0,      dogfight, dogfight, zodiack_state, empty_init, ROT270, "Orca / Thunderbolt",                    "Dog Fight (Thunderbolt)", MACHINE_SUPPORTS_SAVE )
-GAME( 1982, moguchan, 0,      percuss,  moguchan, zodiack_state, empty_init, ROT270, "Orca (Eastern Commerce Inc. license)",  "Mogu Chan (bootleg?)",    MACHINE_WRONG_COLORS | MACHINE_SUPPORTS_SAVE ) // license copyright taken from ROM string at $0b5c
-GAME( 1981, percuss,  0,      percuss,  percuss,  zodiack_state, empty_init, ROT270, "Orca",                                  "The Percussor",           MACHINE_SUPPORTS_SAVE )
-GAME( 1982, bounty,   0,      percuss,  bounty,   zodiack_state, empty_init, ROT180, "Orca",                                  "The Bounty (set 1)",      MACHINE_SUPPORTS_SAVE )
-GAME( 1982, bounty2,  bounty, percuss,  bounty,   zodiack_state, empty_init, ROT180, "Orca",                                  "The Bounty (set 2)",      MACHINE_NOT_WORKING | MACHINE_SUPPORTS_SAVE ) // seems to use a different memory map
+
+/*************************************
+ *
+ *  Game driver(s)
+ *
+ *************************************/
+
+GAME( 1983, zodiack,  0,      zodiack, zodiack,  zodiack_state, empty_init, ROT270, "Orca (Esco Trading Co., Inc. license)", "Zodiack",                 MACHINE_IMPERFECT_COLORS | MACHINE_SUPPORTS_SAVE ) // bullet color needs to be verified
+GAME( 1983, dogfight, 0,      zodiack, dogfight, zodiack_state, empty_init, ROT270, "Orca / Thunderbolt",                    "Dog Fight (Thunderbolt)", MACHINE_SUPPORTS_SAVE )
+GAME( 1982, moguchan, 0,      percuss, moguchan, zodiack_state, empty_init, ROT270, "Orca (Eastern Commerce Inc. license)",  "Mogu Chan (bootleg?)",    MACHINE_WRONG_COLORS | MACHINE_SUPPORTS_SAVE ) // license copyright taken from ROM string at $0b5c
+GAME( 1981, percuss,  0,      percuss, percuss,  zodiack_state, empty_init, ROT270, "Orca",                                  "The Percussor",           MACHINE_SUPPORTS_SAVE )
+GAME( 1982, bounty,   0,      percuss, bounty,   zodiack_state, empty_init, ROT180, "Orca",                                  "The Bounty (set 1)",      MACHINE_SUPPORTS_SAVE )
+GAME( 1982, bounty2,  bounty, percuss, bounty,   zodiack_state, empty_init, ROT180, "Orca",                                  "The Bounty (set 2)",      MACHINE_NOT_WORKING | MACHINE_SUPPORTS_SAVE ) // seems to use a different memory map