diff --git a/sys/pci/if_pcn.c b/sys/pci/if_pcn.c
index 216e17ca967..aa9549e1147 100644
--- a/sys/pci/if_pcn.c
+++ b/sys/pci/if_pcn.c
@@ -111,6 +111,7 @@ static struct pcn_type pcn_devs[] = {
 
 static u_int32_t pcn_csr_read	__P((struct pcn_softc *, int));
 static u_int16_t pcn_csr_read16	__P((struct pcn_softc *, int));
+static u_int16_t pcn_bcr_read16	__P((struct pcn_softc *, int));
 static void pcn_csr_write	__P((struct pcn_softc *, int, int));
 static u_int32_t pcn_bcr_read	__P((struct pcn_softc *, int));
 static void pcn_bcr_write	__P((struct pcn_softc *, int, int));
@@ -229,6 +230,14 @@ static u_int32_t pcn_bcr_read(sc, reg)
 	return(CSR_READ_4(sc, PCN_IO32_BDP));
 }
 
+static u_int16_t pcn_bcr_read16(sc, reg)
+	struct pcn_softc	*sc;
+	int			reg;
+{
+	CSR_WRITE_2(sc, PCN_IO16_RAP, reg);
+	return(CSR_READ_2(sc, PCN_IO16_BDP));
+}
+
 static void pcn_bcr_write(sc, reg, val)
 	struct pcn_softc	*sc;
 	int			reg;
@@ -420,10 +429,30 @@ static int pcn_probe(dev)
 			 * lnc driver's probe routine, the chip will
 			 * be locked into 32-bit operation and the lnc
 			 * driver will be unable to attach to it.
+			 * Note II: if the chip happens to already
+			 * be in 32-bit mode, we still need to check
+			 * the chip ID, but first we have to detect
+			 * 32-bit mode using only 16-bit operations.
+			 * The safest way to do this is to read the
+			 * PCI subsystem ID from BCR23/24 and compare
+			 * that with the value read from PCI config
+			 * space.
 			 */
-			chip_id = pcn_csr_read16(sc, PCN_CSR_CHIPID1);
+			chip_id = pcn_bcr_read16(sc, PCN_BCR_PCISUBSYSID);
 			chip_id <<= 16;
-			chip_id |= pcn_csr_read16(sc, PCN_CSR_CHIPID0);
+			chip_id |= pcn_bcr_read16(sc, PCN_BCR_PCISUBVENID);
+			if (chip_id == pci_read_config(dev,
+			    PCIR_SUBVEND_0, 4)) {
+				/* We're in 16-bit mode. */
+				chip_id = pcn_csr_read16(sc, PCN_CSR_CHIPID1);
+				chip_id <<= 16;
+				chip_id |= pcn_csr_read16(sc, PCN_CSR_CHIPID0);
+			} else {
+				/* We're in 32-bit mode. */
+				chip_id = pcn_csr_read(sc, PCN_CSR_CHIPID1);
+				chip_id <<= 16;
+				chip_id |= pcn_csr_read(sc, PCN_CSR_CHIPID0);
+			}
 			bus_release_resource(dev, PCN_RES,
 			    PCN_RID, sc->pcn_res);
 			PCN_UNLOCK(sc);
diff --git a/sys/pci/if_pcnreg.h b/sys/pci/if_pcnreg.h
index 026c0ea9300..db7c1a3d4e3 100644
--- a/sys/pci/if_pcnreg.h
+++ b/sys/pci/if_pcnreg.h
@@ -247,7 +247,7 @@
 #define PCN_BCR_SSTYLE		0x14
 #define PCN_BCR_PCILAT		0x16
 #define PCN_BCR_PCISUBVENID	0x17
-#define PCN_BCR_PCISUNSYSID	0x18
+#define PCN_BCR_PCISUBSYSID	0x18
 #define PCN_BCR_SRAMSIZE	0x19
 #define PCN_BCR_SRAMBOUND	0x1A
 #define PCN_BCR_SRAMCTL		0x1B