diff --git a/src/devices/bus/s100/dg640.cpp b/src/devices/bus/s100/dg640.cpp
index 18627c97bdf..7f79983f17d 100644
--- a/src/devices/bus/s100/dg640.cpp
+++ b/src/devices/bus/s100/dg640.cpp
@@ -2,11 +2,12 @@
 // copyright-holders:Robbbert
 /***************************************************************************
 
-David Griffiths DG640 board.
+David Griffiths DG640 Video Display Unit.
 
 It was sold by Applied Technology. It uses a MCM6574 as a character generator.
 The DG640 also supports blinking, reverse-video, and LORES graphics.
-It is a S100 card, also known as ETI-640.
+It is a S100 card, originally called "ETI 640" when it was first described
+in the April 1978 issue of Electronics Today International (Australia).
 
 ****************************************************************************/
 
@@ -18,12 +19,13 @@ It is a S100 card, also known as ETI-640.
 
 
 
-DEFINE_DEVICE_TYPE_PRIVATE(S100_DG640, device_s100_card_interface, dg640_device, "dg640", "S100_DG640")
+DEFINE_DEVICE_TYPE(S100_DG640, dg640_device, "dg640", "DG640 VDU")
 
 dg640_device::dg640_device(const machine_config &mconfig, const char *tag, device_t *owner, u32 clock)
 	: device_t(mconfig, S100_DG640, tag, owner, clock)
 	, device_s100_card_interface(mconfig, *this)
 	, m_p_chargen(*this, "chargen")
+	, m_dsw(*this, "DSW")
 {}
 
 void dg640_device::device_start()
@@ -112,7 +114,10 @@ uint32_t dg640_device::screen_update(screen_device &screen, bitmap_ind16 &bitmap
 
 u8 dg640_device::s100_smemr_r(offs_t offset)
 {
-	if ((offset & 0xfc00) == 0)
+	if (m_dsw->read() != (offset & 0xf800) >> 11)
+		return 0xff;
+
+	if ((offset & 0x400) == 0)
 		return m_p_videoram[offset & 0x3ff];
 	else
 		return m_p_attribram[offset & 0x3ff];
@@ -120,13 +125,59 @@ u8 dg640_device::s100_smemr_r(offs_t offset)
 
 void dg640_device::s100_mwrt_w(offs_t offset, u8 data)
 {
-	if ((offset & 0xfc00) == 0)
+	if (m_dsw->read() != (offset & 0xf800) >> 11)
+		return;
+
+	if ((offset & 0x400) == 0)
 		m_p_videoram[offset & 0x3ff] = data;
 	else
 		m_p_attribram[offset & 0x3ff] = data;
 }
 
 
+static INPUT_PORTS_START(dg640)
+	PORT_START("DSW")
+	PORT_DIPNAME(0x1f, 0x0f, "Base Address") PORT_DIPLOCATION("SW1:1,2,3,4,5")
+	PORT_DIPSETTING(0x00, "0000")
+	PORT_DIPSETTING(0x01, "0800")
+	PORT_DIPSETTING(0x02, "1000")
+	PORT_DIPSETTING(0x03, "1800")
+	PORT_DIPSETTING(0x04, "2000")
+	PORT_DIPSETTING(0x05, "2800")
+	PORT_DIPSETTING(0x06, "3000")
+	PORT_DIPSETTING(0x07, "3800")
+	PORT_DIPSETTING(0x08, "4000")
+	PORT_DIPSETTING(0x09, "4800")
+	PORT_DIPSETTING(0x0a, "5000")
+	PORT_DIPSETTING(0x0b, "5800")
+	PORT_DIPSETTING(0x0c, "6000")
+	PORT_DIPSETTING(0x0d, "6800")
+	PORT_DIPSETTING(0x0e, "7000")
+	PORT_DIPSETTING(0x0f, "7800")
+	PORT_DIPSETTING(0x10, "8000")
+	PORT_DIPSETTING(0x11, "8800")
+	PORT_DIPSETTING(0x12, "9000")
+	PORT_DIPSETTING(0x13, "9800")
+	PORT_DIPSETTING(0x14, "A000")
+	PORT_DIPSETTING(0x15, "A800")
+	PORT_DIPSETTING(0x16, "B000")
+	PORT_DIPSETTING(0x17, "B800")
+	PORT_DIPSETTING(0x18, "C000")
+	PORT_DIPSETTING(0x19, "C800")
+	PORT_DIPSETTING(0x1a, "D000")
+	PORT_DIPSETTING(0x1b, "D800")
+	PORT_DIPSETTING(0x1c, "E000")
+	PORT_DIPSETTING(0x1d, "E800")
+	PORT_DIPSETTING(0x1e, "F000")
+	PORT_DIPSETTING(0x1f, "F800")
+INPUT_PORTS_END
+
+ioport_constructor dg640_device::device_input_ports() const
+{
+	return INPUT_PORTS_NAME(dg640);
+}
+
+
 /* F4 Character Displayer */
 static const gfx_layout dg640_charlayout =
 {
@@ -149,11 +200,8 @@ void dg640_device::device_add_mconfig(machine_config &config)
 {
 	screen_device &screen(SCREEN(config, "screen", SCREEN_TYPE_RASTER));
 	screen.set_color(rgb_t::amber());
-	screen.set_refresh_hz(50);
-	screen.set_vblank_time(ATTOSECONDS_IN_USEC(2500)); /* not accurate */
+	screen.set_raw(12_MHz_XTAL, 768, 0, 512, 312, 0, 256); // 15625 Hz horizontal
 	screen.set_screen_update(FUNC(dg640_device::screen_update));
-	screen.set_size(512, 256);
-	screen.set_visarea(0, 511, 0, 255);
 	screen.set_palette("palette");
 
 	GFXDECODE(config, "gfxdecode", "palette", gfx_dg640);
diff --git a/src/devices/bus/s100/dg640.h b/src/devices/bus/s100/dg640.h
index 0ad7dc2e2b0..97d1a3ecbc3 100644
--- a/src/devices/bus/s100/dg640.h
+++ b/src/devices/bus/s100/dg640.h
@@ -22,6 +22,7 @@ public:
 protected:
 	// device-level overrides
 	virtual void device_start() override;
+	virtual ioport_constructor device_input_ports() const override;
 	virtual void device_add_mconfig(machine_config &config) override;
 	virtual const tiny_rom_entry *device_rom_region() const override;
 
@@ -34,6 +35,7 @@ private:
 
 	// object finders
 	required_region_ptr<u8> m_p_chargen;
+	required_ioport m_dsw;
 
 	// internal state
 	std::unique_ptr<u8[]> m_p_videoram;
@@ -42,6 +44,6 @@ private:
 };
 
 
-DECLARE_DEVICE_TYPE(S100_DG640, device_s100_card_interface)
+DECLARE_DEVICE_TYPE(S100_DG640, dg640_device)
 
 #endif // MAME_BUS_S100_DG640_H
diff --git a/src/mame/drivers/binbug.cpp b/src/mame/drivers/binbug.cpp
index 8420ffea6a0..175d513b26d 100644
--- a/src/mame/drivers/binbug.cpp
+++ b/src/mame/drivers/binbug.cpp
@@ -144,12 +144,12 @@ WRITE_LINE_MEMBER( binbug_state::binbug_serial_w )
 
 READ8_MEMBER( binbug_state::mem_r )
 {
-	return m_s100->smemr_r(offset);
+	return m_s100->smemr_r(offset + 0x7800);
 }
 
 WRITE8_MEMBER( binbug_state::mem_w )
 {
-	m_s100->mwrt_w(offset, data);
+	m_s100->mwrt_w(offset + 0x7800, data);
 }
 
 void binbug_state::binbug_mem(address_map &map)
diff --git a/src/mame/drivers/dg680.cpp b/src/mame/drivers/dg680.cpp
index de41ea11621..e583218e32e 100644
--- a/src/mame/drivers/dg680.cpp
+++ b/src/mame/drivers/dg680.cpp
@@ -168,12 +168,12 @@ TIMER_DEVICE_CALLBACK_MEMBER( dg680_state::kansas_r )
 
 READ8_MEMBER( dg680_state::mem_r )
 {
-	return m_s100->smemr_r(offset);
+	return m_s100->smemr_r(offset + 0xf000);
 }
 
 WRITE8_MEMBER( dg680_state::mem_w )
 {
-	m_s100->mwrt_w(offset, data);
+	m_s100->mwrt_w(offset + 0xf000, data);
 }
 
 
@@ -183,7 +183,7 @@ void dg680_state::dg680_mem(address_map &map)
 	map(0x0000, 0xcfff).ram();
 	map(0xd000, 0xd7ff).rom();
 	map(0xd800, 0xefff).ram();
-	map(0xf000, 0xf7ff).rw(FUNC(dg680_state::mem_r),FUNC(dg680_state::mem_w));
+	map(0xf000, 0xffff).rw(FUNC(dg680_state::mem_r),FUNC(dg680_state::mem_w));
 }
 
 void dg680_state::dg680_io(address_map &map)
@@ -261,19 +261,15 @@ WRITE8_MEMBER( dg680_state::port08_w )
 }
 
 
-static DEVICE_INPUT_DEFAULTS_START( keyboard )
-	DEVICE_INPUT_DEFAULTS( "RS232_TXBAUD", 0xff, RS232_BAUD_300 )
-	DEVICE_INPUT_DEFAULTS( "RS232_STARTBITS", 0xff, RS232_STARTBITS_1 )
-	DEVICE_INPUT_DEFAULTS( "RS232_DATABITS", 0xff, RS232_DATABITS_8 )
-	DEVICE_INPUT_DEFAULTS( "RS232_PARITY", 0xff, RS232_PARITY_NONE )
-	DEVICE_INPUT_DEFAULTS( "RS232_STOPBITS", 0xff, RS232_STOPBITS_1 )
-DEVICE_INPUT_DEFAULTS_END
-
 static void dg680_s100_devices(device_slot_interface &device)
 {
 	device.option_add("dg640", S100_DG640);
 }
 
+DEVICE_INPUT_DEFAULTS_START(dg680_dg640_f000)
+	DEVICE_INPUT_DEFAULTS("DSW", 0x1f, 0x1e) // F000-F7FF
+DEVICE_INPUT_DEFAULTS_END
+
 void dg680_state::dg680(machine_config &config)
 {
 	SPEAKER(config, "mono").front_center();
@@ -313,7 +309,8 @@ void dg680_state::dg680(machine_config &config)
 	m_pio->out_pb_callback().set(FUNC(dg680_state::portb_w));
 
 	S100_BUS(config, m_s100, 1_MHz_XTAL);
-	S100_SLOT(config, "s100:1", dg680_s100_devices, "dg640");
+	S100_SLOT(config, "s100:1", dg680_s100_devices, "dg640")
+		.set_option_device_input_defaults("dg640", DEVICE_INPUT_DEFAULTS_NAME(dg680_dg640_f000));
 }
 
 /* ROM definition */