diff --git a/sys/amd64/amd64/mp_machdep.c b/sys/amd64/amd64/mp_machdep.c
index b5bc1fd09022..1155e6751123 100644
--- a/sys/amd64/amd64/mp_machdep.c
+++ b/sys/amd64/amd64/mp_machdep.c
@@ -572,6 +572,7 @@ mp_enable(u_int boot_addr)
 	for (apic = 0; apic < mp_napics; ++apic) {
 		ux = io_apic_read(apic, IOAPIC_VER);
 		io_apic_versions[apic] = ux;
+		io_apic_set_id(apic, IO_TO_ID(apic));
 	}
 
 	/* program each IO APIC in the system */
@@ -1661,13 +1662,7 @@ default_mp_table(int type)
 #else
 	if ((io_apic_id == 0) || (io_apic_id == 1) || (io_apic_id == 15)) {
 #endif	/* REALLY_ANAL_IOAPICID_VALUE */
-		ux = io_apic_read(0, IOAPIC_ID);	/* get current contents */
-		ux &= ~APIC_ID_MASK;	/* clear the ID field */
-		ux |= 0x02000000;	/* set it to '2' */
-		io_apic_write(0, IOAPIC_ID, ux);	/* write new value */
-		ux = io_apic_read(0, IOAPIC_ID);	/* re-read && test */
-		if ((ux & APIC_ID_MASK) != 0x02000000)
-			panic("can't control IO APIC ID, reg: 0x%08x", ux);
+		io_apic_set_id(0, 2);
 		io_apic_id = 2;
 	}
 	IO_TO_ID(0) = io_apic_id;
diff --git a/sys/amd64/amd64/mptable.c b/sys/amd64/amd64/mptable.c
index b5bc1fd09022..1155e6751123 100644
--- a/sys/amd64/amd64/mptable.c
+++ b/sys/amd64/amd64/mptable.c
@@ -572,6 +572,7 @@ mp_enable(u_int boot_addr)
 	for (apic = 0; apic < mp_napics; ++apic) {
 		ux = io_apic_read(apic, IOAPIC_VER);
 		io_apic_versions[apic] = ux;
+		io_apic_set_id(apic, IO_TO_ID(apic));
 	}
 
 	/* program each IO APIC in the system */
@@ -1661,13 +1662,7 @@ default_mp_table(int type)
 #else
 	if ((io_apic_id == 0) || (io_apic_id == 1) || (io_apic_id == 15)) {
 #endif	/* REALLY_ANAL_IOAPICID_VALUE */
-		ux = io_apic_read(0, IOAPIC_ID);	/* get current contents */
-		ux &= ~APIC_ID_MASK;	/* clear the ID field */
-		ux |= 0x02000000;	/* set it to '2' */
-		io_apic_write(0, IOAPIC_ID, ux);	/* write new value */
-		ux = io_apic_read(0, IOAPIC_ID);	/* re-read && test */
-		if ((ux & APIC_ID_MASK) != 0x02000000)
-			panic("can't control IO APIC ID, reg: 0x%08x", ux);
+		io_apic_set_id(0, 2);
 		io_apic_id = 2;
 	}
 	IO_TO_ID(0) = io_apic_id;
diff --git a/sys/amd64/include/mptable.h b/sys/amd64/include/mptable.h
index b5bc1fd09022..1155e6751123 100644
--- a/sys/amd64/include/mptable.h
+++ b/sys/amd64/include/mptable.h
@@ -572,6 +572,7 @@ mp_enable(u_int boot_addr)
 	for (apic = 0; apic < mp_napics; ++apic) {
 		ux = io_apic_read(apic, IOAPIC_VER);
 		io_apic_versions[apic] = ux;
+		io_apic_set_id(apic, IO_TO_ID(apic));
 	}
 
 	/* program each IO APIC in the system */
@@ -1661,13 +1662,7 @@ default_mp_table(int type)
 #else
 	if ((io_apic_id == 0) || (io_apic_id == 1) || (io_apic_id == 15)) {
 #endif	/* REALLY_ANAL_IOAPICID_VALUE */
-		ux = io_apic_read(0, IOAPIC_ID);	/* get current contents */
-		ux &= ~APIC_ID_MASK;	/* clear the ID field */
-		ux |= 0x02000000;	/* set it to '2' */
-		io_apic_write(0, IOAPIC_ID, ux);	/* write new value */
-		ux = io_apic_read(0, IOAPIC_ID);	/* re-read && test */
-		if ((ux & APIC_ID_MASK) != 0x02000000)
-			panic("can't control IO APIC ID, reg: 0x%08x", ux);
+		io_apic_set_id(0, 2);
 		io_apic_id = 2;
 	}
 	IO_TO_ID(0) = io_apic_id;
diff --git a/sys/amd64/include/smp.h b/sys/amd64/include/smp.h
index c11bcb28806f..17b7a3a8172b 100644
--- a/sys/amd64/include/smp.h
+++ b/sys/amd64/include/smp.h
@@ -165,6 +165,7 @@ void	imen_dump		__P((void));
 int	apic_ipi		__P((int, int, int));
 int	selected_apic_ipi	__P((u_int, int, int));
 int	io_apic_setup		__P((int));
+void	io_apic_set_id		__P((int, int));
 int	ext_int_setup		__P((int, int));
 
 #if defined(READY)
diff --git a/sys/i386/i386/mp_machdep.c b/sys/i386/i386/mp_machdep.c
index b5bc1fd09022..1155e6751123 100644
--- a/sys/i386/i386/mp_machdep.c
+++ b/sys/i386/i386/mp_machdep.c
@@ -572,6 +572,7 @@ mp_enable(u_int boot_addr)
 	for (apic = 0; apic < mp_napics; ++apic) {
 		ux = io_apic_read(apic, IOAPIC_VER);
 		io_apic_versions[apic] = ux;
+		io_apic_set_id(apic, IO_TO_ID(apic));
 	}
 
 	/* program each IO APIC in the system */
@@ -1661,13 +1662,7 @@ default_mp_table(int type)
 #else
 	if ((io_apic_id == 0) || (io_apic_id == 1) || (io_apic_id == 15)) {
 #endif	/* REALLY_ANAL_IOAPICID_VALUE */
-		ux = io_apic_read(0, IOAPIC_ID);	/* get current contents */
-		ux &= ~APIC_ID_MASK;	/* clear the ID field */
-		ux |= 0x02000000;	/* set it to '2' */
-		io_apic_write(0, IOAPIC_ID, ux);	/* write new value */
-		ux = io_apic_read(0, IOAPIC_ID);	/* re-read && test */
-		if ((ux & APIC_ID_MASK) != 0x02000000)
-			panic("can't control IO APIC ID, reg: 0x%08x", ux);
+		io_apic_set_id(0, 2);
 		io_apic_id = 2;
 	}
 	IO_TO_ID(0) = io_apic_id;
diff --git a/sys/i386/i386/mpapic.c b/sys/i386/i386/mpapic.c
index 975706ab76ab..7e0f197d0a56 100644
--- a/sys/i386/i386/mpapic.c
+++ b/sys/i386/i386/mpapic.c
@@ -143,6 +143,24 @@ static void polarity __P((int apic, int pin, u_int32_t * flags, int level));
 	  IOART_DESTPHY |	\
 	  IOART_DELLOPRI))
 
+void
+io_apic_set_id(int apic, int id)
+{
+	u_int32_t ux;
+	
+	ux = io_apic_read(apic, IOAPIC_ID);	/* get current contents */
+	if (((ux & APIC_ID_MASK) >> 24) != id) {
+		ux &= ~APIC_ID_MASK;	/* clear the ID field */
+		ux |= (id << 24);
+		io_apic_write(apic, IOAPIC_ID, ux);	/* write new value */
+		ux = io_apic_read(apic, IOAPIC_ID);	/* re-read && test */
+		if (((ux & APIC_ID_MASK) >> 24) != id)
+			panic("can't control IO APIC #%d ID, reg: 0x%08x",
+			      apic, ux);
+	}
+}
+
+
 /*
  * Setup the IO APIC.
  */
diff --git a/sys/i386/i386/mptable.c b/sys/i386/i386/mptable.c
index b5bc1fd09022..1155e6751123 100644
--- a/sys/i386/i386/mptable.c
+++ b/sys/i386/i386/mptable.c
@@ -572,6 +572,7 @@ mp_enable(u_int boot_addr)
 	for (apic = 0; apic < mp_napics; ++apic) {
 		ux = io_apic_read(apic, IOAPIC_VER);
 		io_apic_versions[apic] = ux;
+		io_apic_set_id(apic, IO_TO_ID(apic));
 	}
 
 	/* program each IO APIC in the system */
@@ -1661,13 +1662,7 @@ default_mp_table(int type)
 #else
 	if ((io_apic_id == 0) || (io_apic_id == 1) || (io_apic_id == 15)) {
 #endif	/* REALLY_ANAL_IOAPICID_VALUE */
-		ux = io_apic_read(0, IOAPIC_ID);	/* get current contents */
-		ux &= ~APIC_ID_MASK;	/* clear the ID field */
-		ux |= 0x02000000;	/* set it to '2' */
-		io_apic_write(0, IOAPIC_ID, ux);	/* write new value */
-		ux = io_apic_read(0, IOAPIC_ID);	/* re-read && test */
-		if ((ux & APIC_ID_MASK) != 0x02000000)
-			panic("can't control IO APIC ID, reg: 0x%08x", ux);
+		io_apic_set_id(0, 2);
 		io_apic_id = 2;
 	}
 	IO_TO_ID(0) = io_apic_id;
diff --git a/sys/i386/include/mptable.h b/sys/i386/include/mptable.h
index b5bc1fd09022..1155e6751123 100644
--- a/sys/i386/include/mptable.h
+++ b/sys/i386/include/mptable.h
@@ -572,6 +572,7 @@ mp_enable(u_int boot_addr)
 	for (apic = 0; apic < mp_napics; ++apic) {
 		ux = io_apic_read(apic, IOAPIC_VER);
 		io_apic_versions[apic] = ux;
+		io_apic_set_id(apic, IO_TO_ID(apic));
 	}
 
 	/* program each IO APIC in the system */
@@ -1661,13 +1662,7 @@ default_mp_table(int type)
 #else
 	if ((io_apic_id == 0) || (io_apic_id == 1) || (io_apic_id == 15)) {
 #endif	/* REALLY_ANAL_IOAPICID_VALUE */
-		ux = io_apic_read(0, IOAPIC_ID);	/* get current contents */
-		ux &= ~APIC_ID_MASK;	/* clear the ID field */
-		ux |= 0x02000000;	/* set it to '2' */
-		io_apic_write(0, IOAPIC_ID, ux);	/* write new value */
-		ux = io_apic_read(0, IOAPIC_ID);	/* re-read && test */
-		if ((ux & APIC_ID_MASK) != 0x02000000)
-			panic("can't control IO APIC ID, reg: 0x%08x", ux);
+		io_apic_set_id(0, 2);
 		io_apic_id = 2;
 	}
 	IO_TO_ID(0) = io_apic_id;
diff --git a/sys/i386/include/smp.h b/sys/i386/include/smp.h
index c11bcb28806f..17b7a3a8172b 100644
--- a/sys/i386/include/smp.h
+++ b/sys/i386/include/smp.h
@@ -165,6 +165,7 @@ void	imen_dump		__P((void));
 int	apic_ipi		__P((int, int, int));
 int	selected_apic_ipi	__P((u_int, int, int));
 int	io_apic_setup		__P((int));
+void	io_apic_set_id		__P((int, int));
 int	ext_int_setup		__P((int, int));
 
 #if defined(READY)
diff --git a/sys/kern/subr_smp.c b/sys/kern/subr_smp.c
index b5bc1fd09022..1155e6751123 100644
--- a/sys/kern/subr_smp.c
+++ b/sys/kern/subr_smp.c
@@ -572,6 +572,7 @@ mp_enable(u_int boot_addr)
 	for (apic = 0; apic < mp_napics; ++apic) {
 		ux = io_apic_read(apic, IOAPIC_VER);
 		io_apic_versions[apic] = ux;
+		io_apic_set_id(apic, IO_TO_ID(apic));
 	}
 
 	/* program each IO APIC in the system */
@@ -1661,13 +1662,7 @@ default_mp_table(int type)
 #else
 	if ((io_apic_id == 0) || (io_apic_id == 1) || (io_apic_id == 15)) {
 #endif	/* REALLY_ANAL_IOAPICID_VALUE */
-		ux = io_apic_read(0, IOAPIC_ID);	/* get current contents */
-		ux &= ~APIC_ID_MASK;	/* clear the ID field */
-		ux |= 0x02000000;	/* set it to '2' */
-		io_apic_write(0, IOAPIC_ID, ux);	/* write new value */
-		ux = io_apic_read(0, IOAPIC_ID);	/* re-read && test */
-		if ((ux & APIC_ID_MASK) != 0x02000000)
-			panic("can't control IO APIC ID, reg: 0x%08x", ux);
+		io_apic_set_id(0, 2);
 		io_apic_id = 2;
 	}
 	IO_TO_ID(0) = io_apic_id;
diff --git a/sys/sys/smp.h b/sys/sys/smp.h
index c11bcb28806f..17b7a3a8172b 100644
--- a/sys/sys/smp.h
+++ b/sys/sys/smp.h
@@ -165,6 +165,7 @@ void	imen_dump		__P((void));
 int	apic_ipi		__P((int, int, int));
 int	selected_apic_ipi	__P((u_int, int, int));
 int	io_apic_setup		__P((int));
+void	io_apic_set_id		__P((int, int));
 int	ext_int_setup		__P((int, int));
 
 #if defined(READY)