diff --git a/sys/dev/ofw/ofw_if.m b/sys/dev/ofw/ofw_if.m
index 902f071aa40..d2d323bf4cb 100644
--- a/sys/dev/ofw/ofw_if.m
+++ b/sys/dev/ofw/ofw_if.m
@@ -339,6 +339,13 @@ METHOD void release {
 
 # Commands for returning control to the firmware
 
+/**
+ * @brief Turn off firmware background activities
+ */
+METHOD void quiesce {
+	ofw_t		_ofw;
+};
+
 /**
  * @brief Temporarily return control to firmware.
  */
diff --git a/sys/dev/ofw/ofw_standard.c b/sys/dev/ofw/ofw_standard.c
index e521fa059d3..5eecf773b2b 100644
--- a/sys/dev/ofw/ofw_standard.c
+++ b/sys/dev/ofw/ofw_standard.c
@@ -105,6 +105,7 @@ static ssize_t ofw_std_write(ofw_t ofw, ihandle_t instance, const void *addr,
 static int ofw_std_seek(ofw_t ofw, ihandle_t instance, uint64_t pos);
 static caddr_t ofw_std_claim(ofw_t ofw, void *virt, size_t size, u_int align);
 static void ofw_std_release(ofw_t ofw, void *virt, size_t size);
+static void ofw_std_quiesce(ofw_t ofw);
 static void ofw_std_enter(ofw_t ofw);
 static void ofw_std_exit(ofw_t ofw);
 
@@ -133,6 +134,7 @@ static ofw_method_t ofw_std_methods[] = {
 	OFWMETHOD(ofw_seek,			ofw_std_seek),
 	OFWMETHOD(ofw_claim,			ofw_std_claim),
 	OFWMETHOD(ofw_release,			ofw_std_release),
+	OFWMETHOD(ofw_quiesce,			ofw_std_quiesce),
 	OFWMETHOD(ofw_enter,			ofw_std_enter),
 	OFWMETHOD(ofw_exit,			ofw_std_exit),
 
@@ -730,6 +732,23 @@ ofw_std_release(ofw_t ofw, void *virt, size_t size)
  * Control transfer functions
  */
 
+/* Turn off OF background tasks */
+static void
+ofw_std_quiesce(ofw_t ofw)
+{
+	struct {
+		cell_t name;
+		cell_t nargs;
+		cell_t nreturns;
+	} args = {
+		(cell_t)"quiesce",
+		0,
+		0,
+	};
+
+	openfirmware(&args);
+}
+
 /* Suspend and drop back to the Open Firmware interface. */
 static void
 ofw_std_enter(ofw_t ofw)
diff --git a/sys/dev/ofw/openfirm.c b/sys/dev/ofw/openfirm.c
index 17cda68678a..a560e93770a 100644
--- a/sys/dev/ofw/openfirm.c
+++ b/sys/dev/ofw/openfirm.c
@@ -409,6 +409,15 @@ OF_release(void *virt, size_t size)
  * Control transfer functions
  */
 
+/* Turn off OF background tasks */
+void
+OF_quiesce()
+{
+
+	OFW_QUIESCE(ofw_obj);
+}
+
+
 /* Suspend and drop back to the Open Firmware interface. */
 void
 OF_enter()
diff --git a/sys/dev/ofw/openfirm.h b/sys/dev/ofw/openfirm.h
index 10e8aad80ac..08cbaf3a585 100644
--- a/sys/dev/ofw/openfirm.h
+++ b/sys/dev/ofw/openfirm.h
@@ -133,6 +133,7 @@ void		*OF_claim(void *virtrequest, size_t size, u_int align);
 void		OF_release(void *virt, size_t size);
 
 /* Control transfer functions */
+void		OF_quiesce(void);
 void		OF_enter(void);
 void		OF_exit(void) __attribute__((noreturn));
 
diff --git a/sys/powerpc/aim/ofw_machdep.c b/sys/powerpc/aim/ofw_machdep.c
index 6e98f3e4fba..6a869b4d205 100644
--- a/sys/powerpc/aim/ofw_machdep.c
+++ b/sys/powerpc/aim/ofw_machdep.c
@@ -281,6 +281,8 @@ OF_initial_setup(void *fdt_ptr, void *junk, int (*openfirm)(void *))
 boolean_t
 OF_bootstrap()
 {
+	char model[32];
+	phandle_t rootnode;
 	boolean_t status = FALSE;
 
 	mtx_init(&ofw_mutex, "open firmware", NULL, MTX_DEF);
@@ -295,6 +297,17 @@ OF_bootstrap()
 			return status;
 
 		OF_init(openfirmware);
+
+		/*
+		 * On some machines, we need to quiesce OF to turn off
+		 * background processes.
+		 */
+		rootnode = OF_finddevice("/");
+		if (OF_getprop(rootnode, "model", model, sizeof(model)) > 0) {
+			if (strcmp(model, "PowerMac11,2") == 0 ||
+			    strcmp(model, "PowerMac12,1") == 0)
+				OF_quiesce();
+		}
 	} else {
 		status = OF_install(OFW_FDT, 0);
 
diff --git a/sys/powerpc/ofw/ofw_real.c b/sys/powerpc/ofw/ofw_real.c
index 4425ad1bc5d..1590eb644a3 100644
--- a/sys/powerpc/ofw/ofw_real.c
+++ b/sys/powerpc/ofw/ofw_real.c
@@ -106,6 +106,7 @@ static ssize_t ofw_real_write(ofw_t, ihandle_t instance, const void *addr,
 static int ofw_real_seek(ofw_t, ihandle_t instance, u_int64_t pos);
 static caddr_t ofw_real_claim(ofw_t, void *virt, size_t size, u_int align);
 static void ofw_real_release(ofw_t, void *virt, size_t size);
+static void ofw_real_quiesce(ofw_t);
 static void ofw_real_enter(ofw_t);
 static void ofw_real_exit(ofw_t);
 
@@ -133,6 +134,7 @@ static ofw_method_t ofw_real_methods[] = {
 	OFWMETHOD(ofw_seek,			ofw_real_seek),
 	OFWMETHOD(ofw_claim,			ofw_real_claim),
 	OFWMETHOD(ofw_release,			ofw_real_release),
+	OFWMETHOD(ofw_quiesce,			ofw_real_quiesce),
 	OFWMETHOD(ofw_enter,			ofw_real_enter),
 	OFWMETHOD(ofw_exit,			ofw_real_exit),
 
@@ -889,6 +891,27 @@ ofw_real_release(ofw_t ofw, void *virt, size_t size)
  * Control transfer functions
  */
 
+/* Turn off OF background tasks */
+static void
+ofw_real_quiesce(ofw_t ofw)
+{
+	vm_offset_t argsptr;
+	struct {
+		cell_t name;
+		cell_t nargs;
+		cell_t nreturns;
+	} args;
+
+	args.name = (cell_t)(uintptr_t)"quiesce";
+	args.nargs = 0;
+	args.nreturns = 0;
+
+	ofw_real_start();
+	argsptr = ofw_real_map(&args, sizeof(args));
+	openfirmware((void *)argsptr);
+	ofw_real_stop();
+}
+
 /* Suspend and drop back to the Open Firmware interface. */
 static void
 ofw_real_enter(ofw_t ofw)