diff --git a/sys/isa/isa_common.c b/sys/isa/isa_common.c
index 2003eeb59352..7b3b494de460 100644
--- a/sys/isa/isa_common.c
+++ b/sys/isa/isa_common.c
@@ -23,7 +23,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id$
+ *	$Id: isa_common.c,v 1.1 1999/05/22 15:18:23 dfr Exp $
  */
 /*
  * Modifications for Intel architecture by Garrett A. Wollman.
@@ -109,7 +109,7 @@ isa_attach(device_t dev)
  * Add a new child with default ivars.
  */
 static device_t
-isa_add_child(device_t dev, device_t place, const char *name, int unit)
+isa_add_child(device_t dev, int order, const char *name, int unit)
 {
 	struct	isa_device *idev;
 
@@ -121,10 +121,7 @@ isa_add_child(device_t dev, device_t place, const char *name, int unit)
 	resource_list_init(&idev->id_resources);
 	idev->id_flags = 0;
 
-	if (place)
-		return device_add_child_after(dev, place, name, unit, idev);
-	else
-		return device_add_child(dev, name, unit, idev);
+	return device_add_child_ordered(dev, order, name, unit, idev);
 }
 
 static void
diff --git a/sys/isa/isahint.c b/sys/isa/isahint.c
index c3dff33635a3..25e6d84a42fb 100644
--- a/sys/isa/isahint.c
+++ b/sys/isa/isahint.c
@@ -23,7 +23,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: isahint.c,v 1.1 1999/05/14 11:22:33 dfr Exp $
+ *	$Id: isahint.c,v 1.2 1999/05/22 15:18:26 dfr Exp $
  */
 
 #include <sys/param.h>
@@ -39,7 +39,7 @@ isahint_add_device(device_t parent, const char *name, int unit)
 {
 	device_t	child;
 	int		sensitive, start, count, t;
-	static	device_t last_sensitive;
+	int		order;
 
 	/* device-specific flag overrides any wildcard */
 	sensitive = 0;
@@ -47,13 +47,13 @@ isahint_add_device(device_t parent, const char *name, int unit)
 		resource_int_value(name, -1, "sensitive", &sensitive);
 
 	if (sensitive)
-		child = BUS_ADD_CHILD(parent, last_sensitive, name, unit);
+		order = ISA_ORDER_SENSITIVE;
 	else
-		child = BUS_ADD_CHILD(parent, 0, name, unit);
+		order = ISA_ORDER_SPECULATIVE;
+
+	child = BUS_ADD_CHILD(parent, order, name, unit);
 	if (child == 0)
 		return;
-	else if (sensitive)
-		last_sensitive = child;
 
 	start = 0;
 	count = 0;
diff --git a/sys/isa/isavar.h b/sys/isa/isavar.h
index b8a3a9d998b9..7f397738b1d4 100644
--- a/sys/isa/isavar.h
+++ b/sys/isa/isavar.h
@@ -23,11 +23,22 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: isavar.h,v 1.6 1999/05/14 11:22:35 dfr Exp $
+ *	$Id: isavar.h,v 1.7 1999/05/22 15:18:28 dfr Exp $
  */
 
 #include "isa_if.h"
 
+/*
+ * ISA devices are partially ordered to ensure that devices which are
+ * sensitive to other driver probe routines are probed first. Plug and
+ * Play devices are added after devices with speculative probes so that
+ * the legacy hardware can claim resources allowing the Plug and Play
+ * hardware to choose different resources.
+ */
+#define ISA_ORDER_SENSITIVE	0 /* legacy sensitive hardware */
+#define ISA_ORDER_SPECULATIVE	1 /* legacy non-sensitive hardware */
+#define ISA_ORDER_PNP		2 /* plug-and-play hardware */
+
 #define	ISA_NPORT_IVARS	2
 #define	ISA_NMEM_IVARS	2
 #define	ISA_NIRQ_IVARS	2
diff --git a/sys/kern/bus_if.m b/sys/kern/bus_if.m
index 1a142a184976..63116018e6e2 100644
--- a/sys/kern/bus_if.m
+++ b/sys/kern/bus_if.m
@@ -23,7 +23,7 @@
 # OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 # SUCH DAMAGE.
 #
-#	$Id: bus_if.m,v 1.9 1999/05/10 17:06:12 dfr Exp $
+#	$Id: bus_if.m,v 1.10 1999/05/14 11:22:39 dfr Exp $
 #
 
 INTERFACE bus;
@@ -107,11 +107,11 @@ METHOD void driver_added {
 # For busses which use use drivers supporting DEVICE_IDENTIFY to
 # enumerate their devices, these methods are used to create new
 # device instances. If place is non-NULL, the new device will be
-# added after place in the list of devices.
+# added after the last existing child with the same order.
 #
 METHOD device_t add_child {
 	device_t dev;
-	device_t place;
+	int order;
 	const char *name;
 	int unit;
 };
diff --git a/sys/kern/subr_bus.c b/sys/kern/subr_bus.c
index 7089776fa98b..f4c810ac56c1 100644
--- a/sys/kern/subr_bus.c
+++ b/sys/kern/subr_bus.c
@@ -23,7 +23,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: subr_bus.c,v 1.26 1999/05/22 14:57:15 dfr Exp $
+ *	$Id: subr_bus.c,v 1.27 1999/05/27 07:18:41 dfr Exp $
  */
 
 #include <sys/param.h>
@@ -604,6 +604,7 @@ make_device(device_t parent, const char *name,
     dev->desc = NULL;
     dev->busy = 0;
     dev->flags = DF_ENABLED;
+    dev->order = 0;
     if (unit == -1)
 	dev->flags |= DF_WILDCARD;
     if (name) {
@@ -634,38 +635,40 @@ device_print_child(device_t dev, device_t child)
 device_t
 device_add_child(device_t dev, const char *name, int unit, void *ivars)
 {
-    device_t child;
-
-    PDEBUG(("%s at %s as unit %d with%s ivars",
-    	    name, DEVICENAME(dev), unit, (ivars? "":"out")));
-
-    child = make_device(dev, name, unit, ivars);
-
-    if (child)
-	TAILQ_INSERT_TAIL(&dev->children, child, link);
-    else
-	PDEBUG(("%s failed", name));
-
-    return child;
+    return device_add_child_ordered(dev, 0, name, unit, ivars);
 }
 
 device_t
-device_add_child_after(device_t dev, device_t place, const char *name,
-		       int unit, void *ivars)
+device_add_child_ordered(device_t dev, int order,
+			 const char *name, int unit, void *ivars)
 {
     device_t child;
+    device_t place;
 
-    PDEBUG(("%s at %s after %s as unit %d with%s ivars",
-    	    name, DEVICENAME(dev), DEVICENAME(place), unit, (ivars? "":"out")));
+    PDEBUG(("%s at %s with order %d as unit %d with%s ivars",
+    	    name, DEVICENAME(dev), order, unit, (ivars? "":"out")));
 
     child = make_device(dev, name, unit, ivars);
     if (child == NULL)
 	return child;
+    child->order = order;
+
+    TAILQ_FOREACH(place, &dev->children, link)
+	if (place->order > order)
+	    break;
 
     if (place) {
-	TAILQ_INSERT_AFTER(&dev->children, place, child, link);
+	/*
+	 * The device 'place' is the first device whose order is
+	 * greater than the new child.
+	 */
+	TAILQ_INSERT_BEFORE(place, child, link);
     } else {
-	TAILQ_INSERT_HEAD(&dev->children, child, link);
+	/*
+	 * The new child's order is greater or equal to the order of
+	 * any existing device. Add the child to the tail of the list.
+	 */
+	TAILQ_INSERT_TAIL(&dev->children, child, link);
     }
 
     return child;
diff --git a/sys/sys/bus.h b/sys/sys/bus.h
index d416b6101324..0a5137374077 100644
--- a/sys/sys/bus.h
+++ b/sys/sys/bus.h
@@ -23,7 +23,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: bus.h,v 1.16 1999/05/14 11:22:47 dfr Exp $
+ *	$Id: bus.h,v 1.17 1999/05/22 14:57:13 dfr Exp $
  */
 
 #ifndef _SYS_BUS_H_
@@ -213,8 +213,9 @@ int	bus_teardown_intr(device_t dev, struct resource *r, void *cookie);
  */
 device_t	device_add_child(device_t dev, const char *name, int unit,
 				 void *ivp);
-device_t	device_add_child_after(device_t dev, device_t place,
-				       const char *name, int unit, void *ivp);
+device_t	device_add_child_ordered(device_t dev, int order,
+					 const char *name, int unit,
+					 void *ivp);
 void	device_busy(device_t dev);
 int	device_delete_child(device_t dev, device_t child);
 int	device_detach(device_t dev);
diff --git a/sys/sys/bus_private.h b/sys/sys/bus_private.h
index 770ff6bbaa38..f3539a3d4dac 100644
--- a/sys/sys/bus_private.h
+++ b/sys/sys/bus_private.h
@@ -23,7 +23,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: bus_private.h,v 1.7 1999/05/10 17:06:11 dfr Exp $
+ *	$Id: bus_private.h,v 1.8 1999/05/14 09:13:39 dfr Exp $
  */
 
 #ifndef _SYS_BUS_PRIVATE_H_
@@ -127,16 +127,18 @@ struct device {
     char*		desc;	/* driver specific description */
     int			busy;	/* count of calls to device_busy() */
     device_state_t	state;
-    int			flags;
-#ifdef DEVICE_SYSCTLS
-    struct sysctl_oid	oid[4];
-    struct sysctl_oid_list oidlist[1];
-#endif
+    u_short		flags;
 #define DF_ENABLED	1	/* device should be probed/attached */
 #define DF_FIXEDCLASS	2	/* devclass specified at create time */
 #define DF_WILDCARD	4	/* unit was originally wildcard */
 #define DF_DESCMALLOCED	8	/* description was malloced */
 #define DF_QUIET	16	/* don't print verbose attach message */
+    u_char		order;	/* order from device_add_child_ordered() */
+    u_char		pad;
+#ifdef DEVICE_SYSCTLS
+    struct sysctl_oid	oid[4];
+    struct sysctl_oid_list oidlist[1];
+#endif
     void		*ivars;
     void		*softc;
 };