diff --git a/stand/powerpc/ofw/cas.c b/stand/powerpc/ofw/cas.c
--- a/stand/powerpc/ofw/cas.c
+++ b/stand/powerpc/ofw/cas.c
@@ -232,10 +232,10 @@
 		}
 	}
 
-	if (radix_mmu && (var = getenv("radix_mmu")) != NULL && var[0] != '0')
-		ov5[OV5_MMU_INDEX] = OV5_MMU_RADIX;
-	else
+	if ((var = getenv("radix_mmu")) != NULL && var[0] == '0')
 		radix_mmu = 0;
+	if (radix_mmu)
+		ov5[OV5_MMU_INDEX] = OV5_MMU_RADIX;
 
 	inst = OF_open("/");
 	if (inst == -1) {
diff --git a/sys/powerpc/aim/aim_machdep.c b/sys/powerpc/aim/aim_machdep.c
--- a/sys/powerpc/aim/aim_machdep.c
+++ b/sys/powerpc/aim/aim_machdep.c
@@ -586,8 +586,10 @@
 {
 	if ((cpu_features2 & PPC_FEATURE2_ARCH_3_00) == 0)
 		radix_mmu = 0;
-	else
+	else {
+		radix_mmu = 1;
 		TUNABLE_INT_FETCH("radix_mmu", &radix_mmu);
+	}
 
 	/*
 	 * When using Radix, set the start and end of kva early, to be able to
diff --git a/sys/powerpc/powerpc/pmap_dispatch.c b/sys/powerpc/powerpc/pmap_dispatch.c
--- a/sys/powerpc/powerpc/pmap_dispatch.c
+++ b/sys/powerpc/powerpc/pmap_dispatch.c
@@ -83,7 +83,7 @@
 
 SYSCTL_NODE(_vm, OID_AUTO, pmap, CTLFLAG_RD, 0, "VM/pmap parameters");
 
-int superpages_enabled = 0;
+int superpages_enabled = 1;
 SYSCTL_INT(_vm_pmap, OID_AUTO, superpages_enabled, CTLFLAG_RDTUN,
     &superpages_enabled, 0, "Enable support for transparent superpages");