diff --git a/hw/isa/piix.c b/hw/isa/piix.c
index 55ed997b2c..9e7b11bcdd 100644
--- a/hw/isa/piix.c
+++ b/hw/isa/piix.c
@@ -368,7 +368,8 @@ static const MemoryRegionOps rcr_ops = {
     },
 };
 
-static void pci_piix3_realize(PCIDevice *dev, Error **errp)
+static void pci_piix_realize(PCIDevice *dev, const char *uhci_type,
+                             Error **errp)
 {
     PIIXState *d = PIIX_PCI_DEVICE(dev);
     PCIBus *pci_bus = pci_get_bus(dev);
@@ -408,8 +409,7 @@ static void pci_piix3_realize(PCIDevice *dev, Error **errp)
 
     /* USB */
     if (d->has_usb) {
-        object_initialize_child(OBJECT(dev), "uhci", &d->uhci,
-                                TYPE_PIIX3_USB_UHCI);
+        object_initialize_child(OBJECT(dev), "uhci", &d->uhci, uhci_type);
         qdev_prop_set_int32(DEVICE(&d->uhci), "addr", dev->devfn + 2);
         if (!qdev_realize(DEVICE(&d->uhci), BUS(pci_bus), errp)) {
             return;
@@ -507,7 +507,7 @@ static void piix3_realize(PCIDevice *dev, Error **errp)
     PIIXState *piix3 = PIIX_PCI_DEVICE(dev);
     PCIBus *pci_bus = pci_get_bus(dev);
 
-    pci_piix3_realize(dev, errp);
+    pci_piix_realize(dev, TYPE_PIIX3_USB_UHCI, errp);
     if (*errp) {
         return;
     }
@@ -537,7 +537,7 @@ static void piix3_xen_realize(PCIDevice *dev, Error **errp)
     PIIXState *piix3 = PIIX_PCI_DEVICE(dev);
     PCIBus *pci_bus = pci_get_bus(dev);
 
-    pci_piix3_realize(dev, errp);
+    pci_piix_realize(dev, TYPE_PIIX3_USB_UHCI, errp);
     if (*errp) {
         return;
     }
@@ -568,71 +568,24 @@ static const TypeInfo piix3_xen_info = {
 
 static void piix4_realize(PCIDevice *dev, Error **errp)
 {
+    ERRP_GUARD();
     PIIXState *s = PIIX_PCI_DEVICE(dev);
     PCIBus *pci_bus = pci_get_bus(dev);
     ISABus *isa_bus;
 
-    isa_bus = isa_bus_new(DEVICE(dev), pci_address_space(dev),
-                          pci_address_space_io(dev), errp);
-    if (!isa_bus) {
-        return;
-    }
-
-    memory_region_init_io(&s->rcr_mem, OBJECT(dev), &rcr_ops, s,
-                          "piix-reset-control", 1);
-    memory_region_add_subregion_overlap(pci_address_space_io(dev),
-                                        PIIX_RCR_IOPORT, &s->rcr_mem, 1);
-
-    /* initialize i8259 pic */
-    if (!qdev_realize(DEVICE(&s->pic), BUS(isa_bus), errp)) {
+    pci_piix_realize(dev, TYPE_PIIX4_USB_UHCI, errp);
+    if (*errp) {
         return;
     }
 
-    /* initialize ISA irqs */
-    isa_bus_irqs(isa_bus, s->pic.in_irqs);
+    isa_bus = ISA_BUS(qdev_get_child_bus(DEVICE(dev), "isa.0"));
 
     /* initialize pit */
     i8254_pit_init(isa_bus, 0x40, 0, NULL);
 
-    /* DMA */
-    i8257_dma_init(isa_bus, 0);
-
     /* RTC */
-    qdev_prop_set_int32(DEVICE(&s->rtc), "base_year", 2000);
-    if (!qdev_realize(DEVICE(&s->rtc), BUS(isa_bus), errp)) {
-        return;
-    }
     s->rtc.irq = qdev_get_gpio_in(DEVICE(&s->pic), s->rtc.isairq);
 
-    /* IDE */
-    qdev_prop_set_int32(DEVICE(&s->ide), "addr", dev->devfn + 1);
-    if (!qdev_realize(DEVICE(&s->ide), BUS(pci_bus), errp)) {
-        return;
-    }
-
-    /* USB */
-    if (s->has_usb) {
-        object_initialize_child(OBJECT(dev), "uhci", &s->uhci,
-                                TYPE_PIIX4_USB_UHCI);
-        qdev_prop_set_int32(DEVICE(&s->uhci), "addr", dev->devfn + 2);
-        if (!qdev_realize(DEVICE(&s->uhci), BUS(pci_bus), errp)) {
-            return;
-        }
-    }
-
-    /* ACPI controller */
-    if (s->has_acpi) {
-        object_initialize_child(OBJECT(s), "pm", &s->pm, TYPE_PIIX4_PM);
-        qdev_prop_set_int32(DEVICE(&s->pm), "addr", dev->devfn + 3);
-        qdev_prop_set_uint32(DEVICE(&s->pm), "smb_io_base", s->smb_io_base);
-        qdev_prop_set_bit(DEVICE(&s->pm), "smm-enabled", s->smm_enabled);
-        if (!qdev_realize(DEVICE(&s->pm), BUS(pci_bus), errp)) {
-            return;
-        }
-        qdev_connect_gpio_out(DEVICE(&s->pm), 0,
-                              qdev_get_gpio_in(DEVICE(&s->pic), 9));
-    }
-
     pci_bus_irqs(pci_bus, piix4_set_irq, piix4_pci_slot_get_pirq, s,
                  PIIX_NUM_PIRQS);
 }
