diff --git a/src/devices/machine/68307.cpp b/src/devices/machine/68307.cpp
index ae13e090488..121a729b1fd 100644
--- a/src/devices/machine/68307.cpp
+++ b/src/devices/machine/68307.cpp
@@ -34,11 +34,16 @@ WRITE8_MEMBER(m68307_cpu_device::m68307_internal_serial_w)
 
 
 
-void m68307_cpu_device::m68307_internal_map(address_map &map)
+void m68307_cpu_device::internal_map(address_map &map)
 {
 	map(0x000000f0, 0x000000ff).rw(FUNC(m68307_cpu_device::m68307_internal_base_r), FUNC(m68307_cpu_device::m68307_internal_base_w));
 }
 
+void m68307_cpu_device::cpu_space_map(address_map &map)
+{
+	map(0xfffff0, 0xffffff).r(FUNC(m68307_cpu_device::int_ack)).umask16(0x00ff);
+}
+
 
 void m68307_cpu_device::device_add_mconfig(machine_config &config)
 {
@@ -52,7 +57,7 @@ void m68307_cpu_device::device_add_mconfig(machine_config &config)
 
 
 m68307_cpu_device::m68307_cpu_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
-	: m68000_device(mconfig, tag, owner, clock, M68307, 16, 24, address_map_constructor(FUNC(m68307_cpu_device::m68307_internal_map), this)),
+	: m68000_device(mconfig, tag, owner, clock, M68307, 16, 24, address_map_constructor(FUNC(m68307_cpu_device::internal_map), this)),
 	m_write_irq(*this),
 	m_write_a_tx(*this),
 	m_write_b_tx(*this),
@@ -68,6 +73,8 @@ m68307_cpu_device::m68307_cpu_device(const machine_config &mconfig, const char *
 	m_m68307_scrlow = 0;
 	m_m68307_currentcs = 0;
 	m_ipl = 0;
+
+	m_cpu_space_config.m_internal_map = address_map_constructor(FUNC(m68307_cpu_device::cpu_space_map), this);
 }
 
 
@@ -215,10 +222,10 @@ void m68307_cpu_device::licr2_interrupt()
 		set_ipl(prioritylevel);
 }
 
-IRQ_CALLBACK_MEMBER(m68307_cpu_device::int_ack)
+uint8_t m68307_cpu_device::int_ack(offs_t offset)
 {
-	uint8_t type = m_m68307SIM->get_int_type(this, irqline);
-	logerror("Interrupt acknowledged: level %d, type %01X\n", irqline, type);
+	uint8_t type = m_m68307SIM->get_int_type(this, offset);
+	logerror("Interrupt acknowledged: level %d, type %01X\n", offset, type);
 
 	// UART provides its own vector
 	if (type == 0x0c)
@@ -227,11 +234,6 @@ IRQ_CALLBACK_MEMBER(m68307_cpu_device::int_ack)
 		return (m_m68307SIM->m_pivr & 0xf0) | type;
 }
 
-void m68307_cpu_device::device_config_complete()
-{
-	set_irq_acknowledge_callback(device_irq_acknowledge_delegate(FUNC(m68307_cpu_device::int_ack), this));
-}
-
 void m68307_cpu_device::device_start()
 {
 	init_cpu_m68000();
diff --git a/src/devices/machine/68307.h b/src/devices/machine/68307.h
index 6d5ef10b61c..59698a93d91 100644
--- a/src/devices/machine/68307.h
+++ b/src/devices/machine/68307.h
@@ -36,7 +36,6 @@ protected:
 	class m68307_mbus;
 	class m68307_timer;
 
-	virtual void device_config_complete() override;
 	virtual void device_start() override;
 	virtual void device_reset() override;
 	virtual void device_add_mconfig(machine_config &config) override;
@@ -52,7 +51,7 @@ private:
 	DECLARE_WRITE_LINE_MEMBER(timer1_interrupt);
 	DECLARE_WRITE_LINE_MEMBER(mbus_interrupt);
 
-	IRQ_CALLBACK_MEMBER(int_ack);
+	uint8_t int_ack(offs_t offset);
 
 	DECLARE_WRITE_LINE_MEMBER(m68307_duart_irq_handler);
 	DECLARE_WRITE_LINE_MEMBER(m68307_duart_txa) { m_write_a_tx(state); }
@@ -75,7 +74,8 @@ private:
 	DECLARE_READ8_MEMBER( m68307_internal_mbus_r );
 	DECLARE_WRITE8_MEMBER( m68307_internal_mbus_w );
 
-	void m68307_internal_map(address_map &map);
+	void internal_map(address_map &map);
+	void cpu_space_map(address_map &map);
 
 	devcb_write_line m_write_irq, m_write_a_tx, m_write_b_tx;
 	devcb_read8 m_read_inport;
diff --git a/src/devices/machine/68340.cpp b/src/devices/machine/68340.cpp
index 7f9671fa12d..5e4fc3fc121 100644
--- a/src/devices/machine/68340.cpp
+++ b/src/devices/machine/68340.cpp
@@ -69,21 +69,20 @@ void m68340_cpu_device::update_ipl()
 
 void m68340_cpu_device::internal_vectors_r(address_map &map)
 {
-	map(0xfffff2, 0xffffff).r(FUNC(m68340_cpu_device::int_ack));
+	map(0xfffff0, 0xffffff).r(FUNC(m68340_cpu_device::int_ack)).umask16(0x00ff);
 }
 
 
-u16 m68340_cpu_device::int_ack(offs_t offset)
+uint8_t m68340_cpu_device::int_ack(offs_t offset)
 {
-	int irqline = offset + 1;
-	uint8_t pit_iarb = pit_arbitrate(irqline);
-	uint8_t scu_iarb = m_serial->arbitrate(irqline);
-	uint8_t t1_iarb = m_timer[0]->arbitrate(irqline);
-	uint8_t t2_iarb = m_timer[1]->arbitrate(irqline);
+	uint8_t pit_iarb = pit_arbitrate(offset);
+	uint8_t scu_iarb = m_serial->arbitrate(offset);
+	uint8_t t1_iarb = m_timer[0]->arbitrate(offset);
+	uint8_t t2_iarb = m_timer[1]->arbitrate(offset);
 	uint8_t iarb = std::max({pit_iarb, scu_iarb, t1_iarb, t2_iarb});
-	LOGMASKED(LOG_IPL, "Level %d interrupt arbitration: PIT = %X, SCU = %X, T1 = %X, T2 = %X\n", irqline, pit_iarb, scu_iarb, t1_iarb, t2_iarb);
+	LOGMASKED(LOG_IPL, "Level %d interrupt arbitration: PIT = %X, SCU = %X, T1 = %X, T2 = %X\n", offset, pit_iarb, scu_iarb, t1_iarb, t2_iarb);
 	int response = 0;
-	uint32_t vector = 0x18; // Spurious interrupt
+	uint8_t vector = 0x18; // Spurious interrupt
 
 	// Valid IARB levels are F (high) to 1 (low) and should be unique among modules using the same interrupt level
 	if (iarb != 0)
@@ -118,9 +117,9 @@ u16 m68340_cpu_device::int_ack(offs_t offset)
 	}
 
 	if (response == 0)
-		logerror("Spurious interrupt (level %d)\n", irqline);
+		logerror("Spurious interrupt (level %d)\n", offset);
 	else if (response > 1)
-		logerror("%d modules responded to interrupt (level %d, IARB = %X)\n", response, irqline, iarb);
+		logerror("%d modules responded to interrupt (level %d, IARB = %X)\n", response, offset, iarb);
 
 	return vector;
 }
diff --git a/src/devices/machine/68340.h b/src/devices/machine/68340.h
index 84e51785596..d513320c993 100644
--- a/src/devices/machine/68340.h
+++ b/src/devices/machine/68340.h
@@ -57,7 +57,7 @@ private:
 
 	void update_ipl();
 	void internal_vectors_r(address_map &map);
-	u16 int_ack(offs_t offset);
+	uint8_t int_ack(offs_t offset);
 
 	TIMER_CALLBACK_MEMBER(periodic_interrupt_timer_callback);
 
diff --git a/src/devices/machine/mc68328.cpp b/src/devices/machine/mc68328.cpp
index 9117801749f..4b9e9a8b97e 100644
--- a/src/devices/machine/mc68328.cpp
+++ b/src/devices/machine/mc68328.cpp
@@ -355,7 +355,7 @@ void mc68328_device::internal_map(address_map &map)
 
 void mc68328_device::cpu_space_map(address_map &map)
 {
-	map(0xfffff2, 0xffffff).r(FUNC(mc68328_device::irq_callback));
+	map(0xfffff0, 0xffffff).r(FUNC(mc68328_device::irq_callback)).umask16(0x00ff);
 }
 
 
@@ -387,6 +387,7 @@ mc68328_device::mc68328_device(const machine_config &mconfig, const char *tag, d
 	, m_in_spim_cb(*this)
 	, m_spim_xch_trigger_cb(*this)
 {
+	m_cpu_space_config.m_internal_map = address_map_constructor(FUNC(mc68328_device::cpu_space_map), this);
 }
 
 //-------------------------------------------------
@@ -708,9 +709,9 @@ void mc68328_device::set_port_d_lines(uint8_t state, int bit)
 	poll_port_d_interrupts();
 }
 
-u16 mc68328_device::irq_callback(offs_t offset)
+uint8_t mc68328_device::irq_callback(offs_t offset)
 {
-	return m_regs.ivr | (offset + 1);
+	return m_regs.ivr | offset;
 }
 
 uint32_t mc68328_device::get_timer_frequency(uint32_t index)
diff --git a/src/devices/machine/mc68328.h b/src/devices/machine/mc68328.h
index 36f69f5ab40..8165fbe6e85 100644
--- a/src/devices/machine/mc68328.h
+++ b/src/devices/machine/mc68328.h
@@ -331,7 +331,7 @@ private:
 	void set_interrupt_line(uint32_t line, uint32_t active);
 	void poll_port_d_interrupts();
 	void cpu_space_map(address_map &map);
-	u16 irq_callback(offs_t offset);
+	uint8_t irq_callback(offs_t offset);
 	uint32_t get_timer_frequency(uint32_t index);
 	void maybe_start_timer(uint32_t index, uint32_t new_enable);
 	void timer_compare_event(uint32_t index);
diff --git a/src/devices/machine/mc68901.cpp b/src/devices/machine/mc68901.cpp
index 1b175bbb703..307d5fc6c90 100644
--- a/src/devices/machine/mc68901.cpp
+++ b/src/devices/machine/mc68901.cpp
@@ -344,6 +344,7 @@ mc68901_device::mc68901_device(const machine_config &mconfig, const char *tag, d
 		m_out_so_cb(*this),
 		//m_out_rr_cb(*this),
 		//m_out_tr_cb(*this),
+		m_iack_chain_cb(*this),
 		m_aer(0),
 		m_ier(0),
 		m_gpio_input(0),
@@ -370,6 +371,7 @@ void mc68901_device::device_start()
 	m_out_so_cb.resolve_safe();
 	//m_out_rr_cb.resolve_safe();
 	//m_out_tr_cb.resolve_safe();
+	m_iack_chain_cb.resolve();
 
 	/* create the timers */
 	m_timer[TIMER_A] = timer_alloc(TIMER_A);
@@ -1114,7 +1116,7 @@ WRITE8_MEMBER( mc68901_device::write )
 }
 
 
-u16 mc68901_device::get_vector()
+uint8_t mc68901_device::get_vector()
 {
 	for (int ch = 15; ch >= 0; ch--)
 	{
@@ -1138,7 +1140,10 @@ u16 mc68901_device::get_vector()
 		}
 	}
 
-	return 0x18; // Spurious irq
+	if (!m_iack_chain_cb.isnull())
+		return m_iack_chain_cb();
+	else
+		return 0x18; // Spurious irq
 }
 
 WRITE_LINE_MEMBER( mc68901_device::i0_w ) { gpio_input(0, state); }
diff --git a/src/devices/machine/mc68901.h b/src/devices/machine/mc68901.h
index 4754c24fc6e..93f47ccfd5d 100644
--- a/src/devices/machine/mc68901.h
+++ b/src/devices/machine/mc68901.h
@@ -71,11 +71,12 @@ public:
 	auto out_so_cb() { return m_out_so_cb.bind(); }
 	//auto out_rr_cb() { return m_out_rr_cb.bind(); }
 	//auto out_tr_cb() { return m_out_tr_cb.bind(); }
+	auto iack_chain_cb() { return m_iack_chain_cb.bind(); }
 
 	DECLARE_READ8_MEMBER( read );
 	DECLARE_WRITE8_MEMBER( write );
 
-	u16 get_vector();
+	uint8_t get_vector();
 
 	DECLARE_WRITE_LINE_MEMBER( i0_w );
 	DECLARE_WRITE_LINE_MEMBER( i1_w );
@@ -220,6 +221,8 @@ private:
 	//devcb_write_line        m_out_rr_cb;
 	//devcb_write_line        m_out_tr_cb;
 
+	devcb_read8             m_iack_chain_cb;
+
 	//int m_device_type;                      /* device type */
 
 	/* registers */
diff --git a/src/devices/machine/tmp68301.cpp b/src/devices/machine/tmp68301.cpp
index e21691dfecf..7e2afbe3aca 100644
--- a/src/devices/machine/tmp68301.cpp
+++ b/src/devices/machine/tmp68301.cpp
@@ -200,19 +200,18 @@ void tmp68301_device::device_reset()
 
 void tmp68301_device::internal_vectors_r(address_map &map)
 {
-	map(0xfffff2, 0xffffff).r(FUNC(tmp68301_device::irq_callback));
+	map(0xfffff0, 0xffffff).r(FUNC(tmp68301_device::irq_callback)).umask16(0x00ff);
 }
 
 
-u16 tmp68301_device::irq_callback(offs_t offset)
+uint8_t tmp68301_device::irq_callback(offs_t offset)
 {
-	int irqline = offset + 1;
 	uint8_t IVNR = m_regs[0x9a/2] & 0xe0;      // Interrupt Vector Number Register (IVNR)
 
 	for (int src : { 0, 7, 3, 1, 8, 4, 5, 9, 2 })
 	{
 		// check if the IPL matches
-		if (irqline == (m_icr[src] & 0x07))
+		if (offset == (m_icr[src] & 0x07))
 		{
 			// check if interrupt is pending and not masked out
 			u16 mask = (src > 2 ? 2 : 1) << src;
diff --git a/src/devices/machine/tmp68301.h b/src/devices/machine/tmp68301.h
index 679dd641036..b701822eb78 100644
--- a/src/devices/machine/tmp68301.h
+++ b/src/devices/machine/tmp68301.h
@@ -92,7 +92,7 @@ private:
 	uint8_t m_icr[10];
 
 	void internal_vectors_r(address_map &map);
-	u16 irq_callback(offs_t offset);
+	uint8_t irq_callback(offs_t offset);
 };
 
 DECLARE_DEVICE_TYPE(TMP68301, tmp68301_device)
diff --git a/src/mame/drivers/atarist.cpp b/src/mame/drivers/atarist.cpp
index 53909852226..79c3ffb4f14 100644
--- a/src/mame/drivers/atarist.cpp
+++ b/src/mame/drivers/atarist.cpp
@@ -1219,7 +1219,7 @@ void st_state::ikbd_map(address_map &map)
 void st_state::cpu_space_map(address_map &map)
 {
 	map(0xfffff0, 0xffffff).m(m_maincpu, FUNC(m68000_base_device::autovectors_map));
-	map(0xfffffc, 0xfffffd).r(m_mfp, FUNC(mc68901_device::get_vector));
+	map(0xfffffd, 0xfffffd).r(m_mfp, FUNC(mc68901_device::get_vector));
 }
 
 //-------------------------------------------------
diff --git a/src/mame/drivers/tti.cpp b/src/mame/drivers/tti.cpp
index 0e0c3642858..16e3f606c26 100644
--- a/src/mame/drivers/tti.cpp
+++ b/src/mame/drivers/tti.cpp
@@ -53,6 +53,7 @@ private:
 	IRQ_CALLBACK_MEMBER(intack);
 
 	void prg_map(address_map &map);
+	void fc7_map(address_map &map);
 
 	required_device<cpu_device> m_maincpu;
 	required_device<mc68901_device> m_mfp;
@@ -126,6 +127,11 @@ void tti_state::prg_map(address_map &map)
 	map(0x8007d, 0x8007d).w(FUNC(tti_state::channel_w));
 }
 
+void tti_state::fc7_map(address_map &map)
+{
+	map(0xffff5, 0xffff5).r(m_mfp, FUNC(mc68901_device::get_vector));
+}
+
 static void tti_scsi_devices(device_slot_interface &device)
 {
 	// FIXME: these device options are placeholders
@@ -148,14 +154,14 @@ void tti_state::tti(machine_config &config)
 {
 	M68008(config, m_maincpu, 20_MHz_XTAL / 2); // guess
 	m_maincpu->set_addrmap(AS_PROGRAM, &tti_state::prg_map);
-	m_maincpu->set_irq_acknowledge_callback(FUNC(tti_state::intack));
+	m_maincpu->set_addrmap(m68008_device::AS_CPU_SPACE, &tti_state::fc7_map);
 
 	MC68901(config, m_mfp, 20_MHz_XTAL / 2); // guess
 	m_mfp->set_timer_clock(20_MHz_XTAL / 2); // guess
 	m_mfp->set_rx_clock(9600); // for testing (FIXME: actually 16x)
 	m_mfp->set_tx_clock(9600); // for testing (FIXME: actually 16x)
 	m_mfp->out_so_cb().set("rs232", FUNC(rs232_port_device::write_txd));
-	m_mfp->out_irq_cb().set_inputline("maincpu", M68K_IRQ_5);
+	m_mfp->out_irq_cb().set_inputline("maincpu", M68K_IRQ_2); // probably
 
 	NSCSI_BUS(config, "scsibus");
 	NSCSI_CONNECTOR(config, "scsibus:0", tti_scsi_devices, nullptr);