diff --git a/drivers/ide/pci/sgiioc4.c b/drivers/ide/pci/sgiioc4.c
index 27c9eb9..e125032 100644
--- a/drivers/ide/pci/sgiioc4.c
+++ b/drivers/ide/pci/sgiioc4.c
@@ -723,6 +723,12 @@
 int
 ioc4_ide_attach_one(struct ioc4_driver_data *idd)
 {
+	/* PCI-RT does not bring out IDE connection.
+	 * Do not attach to this particular IOC4.
+	 */
+	if (idd->idd_variant == IOC4_VARIANT_PCI_RT)
+		return 0;
+
 	return pci_init_sgiioc4(idd->idd_pdev,
 				&sgiioc4_chipsets[idd->idd_pci_id->driver_data]);
 }
diff --git a/drivers/serial/ioc4_serial.c b/drivers/serial/ioc4_serial.c
index c620209..717e47bb 100644
--- a/drivers/serial/ioc4_serial.c
+++ b/drivers/serial/ioc4_serial.c
@@ -2646,7 +2646,10 @@
 	struct ioc4_port *port;
 	struct ioc4_soft *soft;
 
+	/* If serial driver did not attach, don't try to detach */
 	control = idd->idd_serial_data;
+	if (!control)
+		return 0;
 
 	for (port_num = 0; port_num < IOC4_NUM_SERIAL_PORTS; port_num++) {
 		for (port_type = UART_PORT_MIN;
@@ -2778,6 +2781,12 @@
 	DPRINT_CONFIG(("%s (0x%p, 0x%p)\n", __FUNCTION__, idd->idd_pdev,
 							idd->idd_pci_id));
 
+	/* PCI-RT does not bring out serial connections.
+	 * Do not attach to this particular IOC4.
+	 */
+	if (idd->idd_variant == IOC4_VARIANT_PCI_RT)
+		return 0;
+
 	/* request serial registers */
 	tmp_addr1 = idd->idd_bar0 + IOC4_SERIAL_OFFSET;
 
diff --git a/drivers/sn/ioc4.c b/drivers/sn/ioc4.c
index cdeff90..8256a97 100644
--- a/drivers/sn/ioc4.c
+++ b/drivers/sn/ioc4.c
@@ -160,9 +160,6 @@
 	writel(0, &idd->idd_misc_regs->int_out.raw);
 	mmiowb();
 
-	printk(KERN_INFO
-	       "%s: Calibrating PCI bus speed "
-	       "for pci_dev %s ... ", __FUNCTION__, pci_name(idd->idd_pdev));
 	/* Set up square wave */
 	int_out.raw = 0;
 	int_out.fields.count = IOC4_CALIBRATE_COUNT;
@@ -206,11 +203,16 @@
 	/* Bounds check the result. */
 	if (period > IOC4_CALIBRATE_LOW_LIMIT ||
 	    period < IOC4_CALIBRATE_HIGH_LIMIT) {
-		printk("failed. Assuming PCI clock ticks are %d ns.\n",
+		printk(KERN_INFO
+		       "IOC4 %s: Clock calibration failed.  Assuming"
+		       "PCI clock is %d ns.\n",
+		       pci_name(idd->idd_pdev),
 		       IOC4_CALIBRATE_DEFAULT / IOC4_EXTINT_COUNT_DIVISOR);
 		period = IOC4_CALIBRATE_DEFAULT;
 	} else {
-		printk("succeeded. PCI clock ticks are %ld ns.\n",
+		printk(KERN_DEBUG
+		       "IOC4 %s: PCI clock is %ld ns.\n",
+		       pci_name(idd->idd_pdev),
 		       period / IOC4_EXTINT_COUNT_DIVISOR);
 	}
 
@@ -222,6 +224,51 @@
 	idd->count_period = period;
 }
 
+/* There are three variants of IOC4 cards: IO9, IO10, and PCI-RT.
+ * Each brings out different combinations of IOC4 signals, thus.
+ * the IOC4 subdrivers need to know to which we're attached.
+ *
+ * We look for the presence of a SCSI (IO9) or SATA (IO10) controller
+ * on the same PCI bus at slot number 3 to differentiate IO9 from IO10.
+ * If neither is present, it's a PCI-RT.
+ */
+static unsigned int
+ioc4_variant(struct ioc4_driver_data *idd)
+{
+	struct pci_dev *pdev = NULL;
+	int found = 0;
+
+	/* IO9: Look for a QLogic ISP 12160 at the same bus and slot 3. */
+	do {
+		pdev = pci_get_device(PCI_VENDOR_ID_QLOGIC,
+				      PCI_DEVICE_ID_QLOGIC_ISP12160, pdev);
+		if (pdev &&
+		    idd->idd_pdev->bus->number == pdev->bus->number &&
+		    3 == PCI_SLOT(pdev->devfn))
+			found = 1;
+		pci_dev_put(pdev);
+	} while (pdev && !found);
+	if (NULL != pdev)
+		return IOC4_VARIANT_IO9;
+
+	/* IO10: Look for a Vitesse VSC 7174 at the same bus and slot 3. */
+	pdev = NULL;
+	do {
+		pdev = pci_get_device(PCI_VENDOR_ID_VITESSE,
+				      PCI_DEVICE_ID_VITESSE_VSC7174, pdev);
+		if (pdev &&
+		    idd->idd_pdev->bus->number == pdev->bus->number &&
+		    3 == PCI_SLOT(pdev->devfn))
+			found = 1;
+		pci_dev_put(pdev);
+	} while (pdev && !found);
+	if (NULL != pdev)
+		return IOC4_VARIANT_IO10;
+
+	/* PCI-RT: No SCSI/SATA controller will be present */
+	return IOC4_VARIANT_PCI_RT;
+}
+
 /* Adds a new instance of an IOC4 card */
 static int
 ioc4_probe(struct pci_dev *pdev, const struct pci_device_id *pci_id)
@@ -286,6 +333,13 @@
 
 	/* Failsafe portion of per-IOC4 initialization */
 
+	/* Detect card variant */
+	idd->idd_variant = ioc4_variant(idd);
+	printk(KERN_INFO "IOC4 %s: %s card detected.\n", pci_name(pdev),
+	       idd->idd_variant == IOC4_VARIANT_IO9 ? "IO9" :
+	       idd->idd_variant == IOC4_VARIANT_PCI_RT ? "PCI-RT" :
+	       idd->idd_variant == IOC4_VARIANT_IO10 ? "IO10" : "unknown");
+
 	/* Initialize IOC4 */
 	pci_read_config_dword(idd->idd_pdev, PCI_COMMAND, &pcmd);
 	pci_write_config_dword(idd->idd_pdev, PCI_COMMAND,
diff --git a/include/linux/ioc4.h b/include/linux/ioc4.h
index 3dd18b7..de73a328 100644
--- a/include/linux/ioc4.h
+++ b/include/linux/ioc4.h
@@ -147,6 +147,10 @@
 #define IOC4_GPCR_EDGE_6 0x40
 #define IOC4_GPCR_EDGE_7 0x80
 
+#define IOC4_VARIANT_IO9	0x0900
+#define IOC4_VARIANT_PCI_RT	0x0901
+#define IOC4_VARIANT_IO10	0x1000
+
 /* One of these per IOC4 */
 struct ioc4_driver_data {
 	struct list_head idd_list;
@@ -156,6 +160,7 @@
 	struct __iomem ioc4_misc_regs *idd_misc_regs;
 	unsigned long count_period;
 	void *idd_serial_data;
+	unsigned int idd_variant;
 };
 
 /* One per submodule */