diff --git a/drivers/scsi/aic7xxx/aic7xxx_osm.c b/drivers/scsi/aic7xxx/aic7xxx_osm.c
index e5bb4d8..0b3c01a 100644
--- a/drivers/scsi/aic7xxx/aic7xxx_osm.c
+++ b/drivers/scsi/aic7xxx/aic7xxx_osm.c
@@ -2539,15 +2539,23 @@
 static void ahc_linux_get_signalling(struct Scsi_Host *shost)
 {
 	struct ahc_softc *ahc = *(struct ahc_softc **)shost->hostdata;
-	u8 mode = ahc_inb(ahc, SBLKCTL);
+	u8 mode;
 
-	if (mode & ENAB40)
-		spi_signalling(shost) = SPI_SIGNAL_LVD;
-	else if (mode & ENAB20)
+	if (!(ahc->features & AHC_ULTRA2)) {
+		/* non-LVD chipset, may not have SBLKCTL reg */
 		spi_signalling(shost) = 
 			ahc->features & AHC_HVD ?
 			SPI_SIGNAL_HVD :
 			SPI_SIGNAL_SE;
+		return;
+	}
+
+	mode = ahc_inb(ahc, SBLKCTL);
+
+	if (mode & ENAB40)
+		spi_signalling(shost) = SPI_SIGNAL_LVD;
+	else if (mode & ENAB20)
+		spi_signalling(shost) = SPI_SIGNAL_SE;
 	else
 		spi_signalling(shost) = SPI_SIGNAL_UNKNOWN;
 }