diff --git a/hw/ppc/ppc405_boards.c b/hw/ppc/ppc405_boards.c
index 057882a5d2..de93c40f1a 100644
--- a/hw/ppc/ppc405_boards.c
+++ b/hw/ppc/ppc405_boards.c
@@ -170,8 +170,8 @@ static void ref405ep_init(MachineState *machine)
     }
 
     /* XXX: fix this */
-    memory_region_allocate_system_memory(&ram_memories[0], NULL, "ef405ep.ram",
-                                         machine->ram_size);
+    memory_region_init_alias(&ram_memories[0], NULL, "ef405ep.ram.alias",
+                             machine->ram, 0, machine->ram_size);
     ram_bases[0] = 0;
     ram_sizes[0] = machine->ram_size;
     memory_region_init(&ram_memories[1], NULL, "ef405ep.ram1", 0);
@@ -312,6 +312,7 @@ static void ref405ep_class_init(ObjectClass *oc, void *data)
     mc->desc = "ref405ep";
     mc->init = ref405ep_init;
     mc->default_ram_size = 0x08000000;
+    mc->default_ram_id = "ef405ep.ram";
 }
 
 static const TypeInfo ref405ep_type = {
@@ -424,7 +425,6 @@ static void taihu_405ep_init(MachineState *machine)
     MemoryRegion *sysmem = get_system_memory();
     MemoryRegion *bios;
     MemoryRegion *ram_memories = g_new(MemoryRegion, 2);
-    MemoryRegion *ram = g_malloc0(sizeof(*ram));
     hwaddr ram_bases[2], ram_sizes[2];
     long bios_size;
     target_ulong kernel_base, initrd_base;
@@ -439,18 +439,16 @@ static void taihu_405ep_init(MachineState *machine)
         g_free(sz);
         exit(EXIT_FAILURE);
     }
-    memory_region_allocate_system_memory(ram, NULL, "taihu_405ep.ram",
-                                         machine->ram_size);
 
     ram_bases[0] = 0;
     ram_sizes[0] = 0x04000000;
     memory_region_init_alias(&ram_memories[0], NULL,
-                             "taihu_405ep.ram-0", ram, ram_bases[0],
+                             "taihu_405ep.ram-0", machine->ram, ram_bases[0],
                              ram_sizes[0]);
     ram_bases[1] = 0x04000000;
     ram_sizes[1] = 0x04000000;
     memory_region_init_alias(&ram_memories[1], NULL,
-                             "taihu_405ep.ram-1", ram, ram_bases[1],
+                             "taihu_405ep.ram-1", machine->ram, ram_bases[1],
                              ram_sizes[1]);
     ppc405ep_init(sysmem, ram_memories, ram_bases, ram_sizes,
                   33333333, &pic, kernel_filename == NULL ? 0 : 1);
@@ -546,6 +544,7 @@ static void taihu_class_init(ObjectClass *oc, void *data)
     mc->desc = "taihu";
     mc->init = taihu_405ep_init;
     mc->default_ram_size = 0x08000000;
+    mc->default_ram_id = "taihu_405ep.ram";
 }
 
 static const TypeInfo taihu_type = {