Index: head/sys/arm/arm/nexus.c
===================================================================
--- head/sys/arm/arm/nexus.c
+++ head/sys/arm/arm/nexus.c
@@ -161,10 +161,11 @@
 {
 
 	mem_rman.rm_start = 0;
-	mem_rman.rm_end = ~0ul;
+	mem_rman.rm_end = BUS_SPACE_MAXADDR;
 	mem_rman.rm_type = RMAN_ARRAY;
 	mem_rman.rm_descr = "I/O memory addresses";
-	if (rman_init(&mem_rman) || rman_manage_region(&mem_rman, 0, ~0))
+	if (rman_init(&mem_rman) ||
+	    rman_manage_region(&mem_rman, 0, BUS_SPACE_MAXADDR))
 		panic("nexus_probe mem_rman");
 
 	/*
Index: head/sys/arm64/arm64/nexus.c
===================================================================
--- head/sys/arm64/arm64/nexus.c
+++ head/sys/arm64/arm64/nexus.c
@@ -153,13 +153,14 @@
 {
 
 	mem_rman.rm_start = 0;
-	mem_rman.rm_end = ~0ul;
+	mem_rman.rm_end = BUS_SPACE_MAXADDR;
 	mem_rman.rm_type = RMAN_ARRAY;
 	mem_rman.rm_descr = "I/O memory addresses";
-	if (rman_init(&mem_rman) || rman_manage_region(&mem_rman, 0, ~0))
+	if (rman_init(&mem_rman) ||
+	    rman_manage_region(&mem_rman, 0, BUS_SPACE_MAXADDR))
 		panic("nexus_attach mem_rman");
 	irq_rman.rm_start = 0;
-	irq_rman.rm_end = ~0ul;
+	irq_rman.rm_end = ~0;
 	irq_rman.rm_type = RMAN_ARRAY;
 	irq_rman.rm_descr = "Interrupts";
 	if (rman_init(&irq_rman) || rman_manage_region(&irq_rman, 0, ~0))
Index: head/sys/mips/mips/nexus.c
===================================================================
--- head/sys/mips/mips/nexus.c
+++ head/sys/mips/mips/nexus.c
@@ -185,11 +185,11 @@
 	}
 
 	mem_rman.rm_start = 0;
-	mem_rman.rm_end = ~0ul;
+	mem_rman.rm_end = BUS_SPACE_MAXADDR;
 	mem_rman.rm_type = RMAN_ARRAY;
 	mem_rman.rm_descr = "Memory addresses";
 	if (rman_init(&mem_rman) != 0 ||
-	    rman_manage_region(&mem_rman, 0, ~0) != 0) {
+	    rman_manage_region(&mem_rman, 0, BUS_SPACE_MAXADDR) != 0) {
 		panic("%s: mem_rman", __func__);
 	}
 
Index: head/sys/riscv/riscv/nexus.c
===================================================================
--- head/sys/riscv/riscv/nexus.c
+++ head/sys/riscv/riscv/nexus.c
@@ -143,13 +143,14 @@
 {
 
 	mem_rman.rm_start = 0;
-	mem_rman.rm_end = ~0ul;
+	mem_rman.rm_end = BUS_SPACE_MAXADDR;
 	mem_rman.rm_type = RMAN_ARRAY;
 	mem_rman.rm_descr = "I/O memory addresses";
-	if (rman_init(&mem_rman) || rman_manage_region(&mem_rman, 0, ~0))
+	if (rman_init(&mem_rman) ||
+	    rman_manage_region(&mem_rman, 0, BUS_SPACE_MAXADDR))
 		panic("nexus_attach mem_rman");
 	irq_rman.rm_start = 0;
-	irq_rman.rm_end = ~0ul;
+	irq_rman.rm_end = ~0;
 	irq_rman.rm_type = RMAN_ARRAY;
 	irq_rman.rm_descr = "Interrupts";
 	if (rman_init(&irq_rman) || rman_manage_region(&irq_rman, 0, ~0))
Index: head/sys/sparc64/sparc64/nexus.c
===================================================================
--- head/sys/sparc64/sparc64/nexus.c
+++ head/sys/sparc64/sparc64/nexus.c
@@ -233,7 +233,7 @@
 		    rman_init(&sc->sc_mem_rman) != 0 ||
 		    rman_manage_region(&sc->sc_intr_rman, 0,
 		    IV_MAX - 1) != 0 ||
-		    rman_manage_region(&sc->sc_mem_rman, 0ULL, ~0ULL) != 0)
+		    rman_manage_region(&sc->sc_mem_rman, 0, BUS_SPACE_MAXADDR) != 0)
 			panic("%s: failed to set up rmans.", __func__);
 	} else
 		node = ofw_bus_get_node(dev);
Index: head/sys/x86/x86/nexus.c
===================================================================
--- head/sys/x86/x86/nexus.c
+++ head/sys/x86/x86/nexus.c
@@ -261,11 +261,15 @@
 		panic("nexus_init_resources port_rman");
 
 	mem_rman.rm_start = 0;
-	mem_rman.rm_end = ~0ul;
+#ifndef PAE
+	mem_rman.rm_end = BUS_SPACE_MAXADDR;
+#else
+	mem_rman.rm_end = ((1ULL << cpu_maxphyaddr) - 1);
+#endif
 	mem_rman.rm_type = RMAN_ARRAY;
 	mem_rman.rm_descr = "I/O memory addresses";
 	if (rman_init(&mem_rman)
-	    || rman_manage_region(&mem_rman, 0, ~0))
+	    || rman_manage_region(&mem_rman, 0, mem_rman.rm_end))
 		panic("nexus_init_resources mem_rman");
 }