diff --git a/src/devices/machine/genpc.cpp b/src/devices/machine/genpc.cpp
index 12457166cc6..6aa7524d383 100644
--- a/src/devices/machine/genpc.cpp
+++ b/src/devices/machine/genpc.cpp
@@ -494,7 +494,7 @@ ioport_constructor ibm5160_mb_device::device_input_ports() const
 void ibm5160_mb_device::static_set_cputag(device_t &device, const char *tag)
 {
 	ibm5160_mb_device &board = downcast<ibm5160_mb_device &>(device);
-	board.m_cputag = tag;
+	board.m_maincpu.set_tag(tag);
 }
 
 //**************************************************************************
@@ -517,7 +517,7 @@ ibm5160_mb_device::ibm5160_mb_device(
 		device_t *owner,
 		uint32_t clock)
 	: device_t(mconfig, type, tag, owner, clock)
-	, m_maincpu(*owner, "maincpu")
+	, m_maincpu(*this, finder_base::DUMMY_TAG)
 	, m_pic8259(*this, "pic8259")
 	, m_pit8253(*this, "pit8253")
 	, m_dma8237(*this, "dma8237")
diff --git a/src/devices/machine/genpc.h b/src/devices/machine/genpc.h
index c3e53283e75..ce5f393395e 100644
--- a/src/devices/machine/genpc.h
+++ b/src/devices/machine/genpc.h
@@ -25,7 +25,7 @@
 
 #define MCFG_IBM5160_MOTHERBOARD_ADD(_tag, _cputag) \
 	MCFG_DEVICE_ADD(_tag, IBM5160_MOTHERBOARD, 0) \
-	ibm5160_mb_device::static_set_cputag(*device, _cputag);
+	ibm5160_mb_device::static_set_cputag(*device, "^" _cputag);
 // ======================> ibm5160_mb_device
 class ibm5160_mb_device : public device_t
 {
@@ -116,8 +116,6 @@ protected:
 	DECLARE_WRITE_LINE_MEMBER( pc_dack2_w );
 	DECLARE_WRITE_LINE_MEMBER( pc_dack3_w );
 
-	const char *m_cputag;
-
 	void pc_select_dma_channel(int channel, bool state);
 };
 
@@ -128,7 +126,7 @@ DECLARE_DEVICE_TYPE(IBM5160_MOTHERBOARD, ibm5160_mb_device)
 
 #define MCFG_IBM5150_MOTHERBOARD_ADD(_tag, _cputag) \
 	MCFG_DEVICE_ADD(_tag, IBM5150_MOTHERBOARD, 0) \
-	ibm5150_mb_device::static_set_cputag(*device, _cputag);
+	ibm5150_mb_device::static_set_cputag(*device, "^" _cputag);
 
 // ======================> ibm5150_mb_device
 class ibm5150_mb_device : public ibm5160_mb_device
@@ -160,7 +158,7 @@ DECLARE_DEVICE_TYPE(IBM5150_MOTHERBOARD, ibm5150_mb_device)
 
 #define MCFG_EC1841_MOTHERBOARD_ADD(_tag, _cputag) \
 	MCFG_DEVICE_ADD(_tag, EC1841_MOTHERBOARD, 0) \
-	ec1841_mb_device::static_set_cputag(*device, _cputag);
+	ec1841_mb_device::static_set_cputag(*device, "^" _cputag);
 
 class ec1841_mb_device : public ibm5160_mb_device
 {
@@ -185,7 +183,7 @@ DECLARE_DEVICE_TYPE(EC1841_MOTHERBOARD, ec1841_mb_device)
 
 #define MCFG_PCNOPPI_MOTHERBOARD_ADD(_tag, _cputag) \
 	MCFG_DEVICE_ADD(_tag, PCNOPPI_MOTHERBOARD, 0) \
-	pc_noppi_mb_device::static_set_cputag(*device, _cputag);
+	pc_noppi_mb_device::static_set_cputag(*device, "^" _cputag);
 
 class pc_noppi_mb_device : public ibm5160_mb_device
 {
diff --git a/src/mame/drivers/asst128.cpp b/src/mame/drivers/asst128.cpp
index 67f2c7b5d01..70f091da1de 100644
--- a/src/mame/drivers/asst128.cpp
+++ b/src/mame/drivers/asst128.cpp
@@ -99,7 +99,7 @@ static MACHINE_CONFIG_START( asst128 )
 	MCFG_CPU_IRQ_ACKNOWLEDGE_DEVICE("mb:pic8259", pic8259_device, inta_cb)
 
 	MCFG_DEVICE_ADD("mb", ASST128_MOTHERBOARD, 0)
-	asst128_mb_device::static_set_cputag(*device, "maincpu");
+	asst128_mb_device::static_set_cputag(*device, "^maincpu");
 	MCFG_DEVICE_INPUT_DEFAULTS(asst128)
 
 	MCFG_DEVICE_MODIFY("mb:cassette")
diff --git a/src/mame/drivers/tandy1t.cpp b/src/mame/drivers/tandy1t.cpp
index 77fb2d00076..b8a94e58c69 100644
--- a/src/mame/drivers/tandy1t.cpp
+++ b/src/mame/drivers/tandy1t.cpp
@@ -622,7 +622,7 @@ GFXDECODE_END
 
 static MACHINE_CONFIG_START(tandy1000_common)
 	MCFG_DEVICE_ADD("mb", T1000_MOTHERBOARD, 0)
-	t1000_mb_device::static_set_cputag(*device, "maincpu");
+	t1000_mb_device::static_set_cputag(*device, "^maincpu");
 
 	/* video hardware */
 	MCFG_PCVIDEO_T1000_ADD("pcvideo_t1000")