diff --git a/sys/dev/mlx/mlx.c b/sys/dev/mlx/mlx.c
index d353ada28e9..95b83c9a216 100644
--- a/sys/dev/mlx/mlx.c
+++ b/sys/dev/mlx/mlx.c
@@ -72,7 +72,7 @@ static struct cdevsw mlx_cdevsw = {
 		/* dump */	nodump,
 		/* psize */ 	nopsize,
 		/* flags */	0,
-		/* bmaj */	254	/* XXX magic no-bdev */
+		/* bmaj */	-1
 };
 
 static int	cdev_registered = 0;
@@ -85,6 +85,10 @@ static int			mlx_v3_tryqueue(struct mlx_softc *sc, struct mlx_command *mc);
 static int			mlx_v3_findcomplete(struct mlx_softc *sc, u_int8_t *slot, u_int16_t *status);
 static void			mlx_v3_intaction(struct mlx_softc *sc, int action);
 
+static int			mlx_v4_tryqueue(struct mlx_softc *sc, struct mlx_command *mc);
+static int			mlx_v4_findcomplete(struct mlx_softc *sc, u_int8_t *slot, u_int16_t *status);
+static void			mlx_v4_intaction(struct mlx_softc *sc, int action);
+
 /*
  * Status monitoring
  */
@@ -287,6 +291,11 @@ mlx_attach(struct mlx_softc *sc)
 	sc->mlx_findcomplete	= mlx_v3_findcomplete;
 	sc->mlx_intaction	= mlx_v3_intaction;
 	break;
+    case MLX_IFTYPE_4:
+	sc->mlx_tryqueue	= mlx_v4_tryqueue;
+	sc->mlx_findcomplete	= mlx_v4_findcomplete;
+	sc->mlx_intaction	= mlx_v4_intaction;
+	break;
     default:
 	device_printf(sc->mlx_dev, "attaching unsupported interface version %d\n", sc->mlx_iftype);
 	return(ENXIO);		/* should never happen */
@@ -380,11 +389,19 @@ mlx_attach(struct mlx_softc *sc)
      */
     switch(sc->mlx_iftype) {
     case MLX_IFTYPE_3:
+	/* XXX certify 3.52? */
 	if (sc->mlx_fwminor != 51) {
 	    device_printf(sc->mlx_dev, " *** WARNING *** This firmware revision is NOT SUPPORTED\n");
 	    device_printf(sc->mlx_dev, " *** WARNING *** Use revision 3.51 only\n");
 	}
 	break;
+    case MLX_IFTYPE_4:
+	/* XXX certify firmware versions? */
+	if (sc->mlx_fwminor != 6) {
+	    device_printf(sc->mlx_dev, " *** WARNING *** This firmware revision is NOT SUPPORTED\n");
+	    device_printf(sc->mlx_dev, " *** WARNING *** Use revision 4.6 only\n");
+	}
+	break;
     default:
 	device_printf(sc->mlx_dev, "interface version corrupted to %d\n", sc->mlx_iftype);
 	return(ENXIO);		/* should never happen */
@@ -450,7 +467,7 @@ mlx_startup(struct mlx_softc *sc)
     	if (dr->ms_disk == 0) {
 	    /* pick up drive information */
 	    dr->ms_size = mes[i].sd_size;
-	    dr->ms_raidlevel = mes[i].sd_raidlevel;
+	    dr->ms_raidlevel = mes[i].sd_raidlevel & 0xf;
 	    dr->ms_state = mes[i].sd_state;
 
 	    /* generate geometry information */
@@ -619,9 +636,6 @@ mlx_intr(void *arg)
 
     debug("called");
 
-    /* ack the interrupt */
-    sc->mlx_intaction(sc, MLX_INTACTION_ACKNOWLEDGE);
-
     /* spin collecting finished commands */
     worked = 0;
     while (mlx_done(sc))
@@ -937,7 +951,7 @@ mlx_periodic(void *data)
     } else if (MLX_PERIODIC_ISBUSY(sc)) {
 
 	/* time to perform a periodic status poll? XXX tuneable interval? */
-	if (time_second > (sc->mlx_lastpoll + 5)) {
+	if (time_second > (sc->mlx_lastpoll + 10)) {
 	    sc->mlx_lastpoll = time_second;
 
 	    /* for caution's sake */
@@ -1602,7 +1616,7 @@ mlx_startio(struct mlx_softc *sc)
 	mlx_mapcmd(mc);
 	
 	/* build a suitable I/O command (assumes 512-byte rounded transfers) */
-	mlxd = (struct mlxd_softc *)bp->b_driver1;
+	mlxd = (struct mlxd_softc *)bp->b_dev->si_drv1;
 	driveno = mlxd->mlxd_drive - &sc->mlx_sysdrive[0];
 	blkcount = bp->b_bcount / MLX_BLKSIZE;
 
@@ -1639,7 +1653,7 @@ mlx_completeio(struct mlx_command *mc)
 {
     struct mlx_softc	*sc = mc->mc_sc;
     struct buf		*bp = (struct buf *)mc->mc_private;
-    struct mlxd_softc	*mlxd = (struct mlxd_softc *)bp->b_driver1;
+    struct mlxd_softc	*mlxd = (struct mlxd_softc *)bp->b_dev->si_drv1;
     
     if (mc->mc_status != MLX_STATUS_OK) {	/* could be more verbose here? */
 	bp->b_error = EIO;
@@ -1649,6 +1663,7 @@ mlx_completeio(struct mlx_command *mc)
 	case MLX_STATUS_RDWROFFLINE:		/* system drive has gone offline */
 	    device_printf(mlxd->mlxd_dev, "drive offline\n");
 	    device_printf(sc->mlx_dev, "drive offline\n");
+	    /* should signal this with a return code */
 	    mlxd->mlxd_drive->ms_state = MLX_SYSD_OFFLINE;
 	    break;
 
@@ -2113,7 +2128,7 @@ mlx_v3_tryqueue(struct mlx_softc *sc, struct mlx_command *mc)
 	    MLX_V3_PUT_MAILBOX(sc, i, mc->mc_mailbox[i]);
 	
 	/* post command */
-	MLX_V3_PUT_IDBR(sc, MLX_V3_GET_IDBR(sc) | MLX_V3_IDB_FULL);
+	MLX_V3_PUT_IDBR(sc, MLX_V3_IDB_FULL);
 	return(1);
     }
     return(0);
@@ -2137,8 +2152,8 @@ mlx_v3_findcomplete(struct mlx_softc *sc, u_int8_t *slot, u_int16_t *status)
 	*status = MLX_V3_GET_STATUS(sc);		/* get status */
 
 	/* acknowledge completion */
-	MLX_V3_PUT_ODBR(sc, MLX_V3_GET_ODBR(sc) | MLX_V3_ODB_SAVAIL);
-	MLX_V3_PUT_IDBR(sc, MLX_V3_GET_IDBR(sc) | MLX_V3_IDB_SACK);
+	MLX_V3_PUT_ODBR(sc, MLX_V3_ODB_SAVAIL);
+	MLX_V3_PUT_IDBR(sc, MLX_V3_IDB_SACK);
 	return(1);
     }
     return(0);
@@ -2167,6 +2182,86 @@ mlx_v3_intaction(struct mlx_softc *sc, int action)
 }
 
 
+/********************************************************************************
+ ********************************************************************************
+                                                Type 4 interface accessor methods
+ ********************************************************************************
+ ********************************************************************************/
+
+/********************************************************************************
+ * Try to give (mc) to the controller.  Returns 1 if successful, 0 on failure
+ * (the controller is not ready to take a command).
+ *
+ * Must be called at splbio or in a fashion that prevents reentry.
+ */
+static int
+mlx_v4_tryqueue(struct mlx_softc *sc, struct mlx_command *mc)
+{
+    int		i;
+    
+    debug("called");
+
+    /* ready for our command? */
+    if (!(MLX_V4_GET_IDBR(sc) & MLX_V4_IDB_FULL)) {
+	/* copy mailbox data to window */
+	for (i = 0; i < 13; i++)
+	    MLX_V4_PUT_MAILBOX(sc, i, mc->mc_mailbox[i]);
+	
+	/* post command */
+	MLX_V4_PUT_IDBR(sc, MLX_V4_IDB_HWMBOX_CMD);
+	return(1);
+    }
+    return(0);
+}
+
+/********************************************************************************
+ * See if a command has been completed, if so acknowledge its completion
+ * and recover the slot number and status code.
+ *
+ * Must be called at splbio or in a fashion that prevents reentry.
+ */
+static int
+mlx_v4_findcomplete(struct mlx_softc *sc, u_int8_t *slot, u_int16_t *status)
+{
+
+    debug("called");
+
+    /* status available? */
+    if (MLX_V4_GET_ODBR(sc) & MLX_V4_ODB_HWSAVAIL) {
+	*slot = MLX_V4_GET_STATUS_IDENT(sc);		/* get command identifier */
+	*status = MLX_V4_GET_STATUS(sc);		/* get status */
+
+	/* acknowledge completion */
+	MLX_V4_PUT_ODBR(sc, MLX_V4_ODB_HWMBOX_ACK);
+	MLX_V4_PUT_IDBR(sc, MLX_V4_IDB_SACK);
+	return(1);
+    }
+    return(0);
+}
+
+/********************************************************************************
+ * Enable/disable interrupts as requested.
+ *
+ * Must be called at splbio or in a fashion that prevents reentry.
+ */
+static void
+mlx_v4_intaction(struct mlx_softc *sc, int action)
+{
+    debug("called");
+
+    switch(action) {
+    case MLX_INTACTION_DISABLE:
+	MLX_V4_PUT_IER(sc, MLX_V4_IER_MASK | MLX_V4_IER_DISINT);
+	sc->mlx_state &= ~MLX_STATE_INTEN;
+	break;
+    case MLX_INTACTION_ENABLE:
+	MLX_V4_PUT_IER(sc, MLX_V4_IER_MASK & ~MLX_V4_IER_DISINT);
+	sc->mlx_state |= MLX_STATE_INTEN;
+	break;
+    }
+}
+
+
 /********************************************************************************
  ********************************************************************************
                                                                         Debugging
@@ -2258,6 +2353,9 @@ mlx_name_controller(u_int32_t hwid)
     case 0x10:
 	submodel = "PG";
 	break;
+    case 0x11:
+	submodel = "PJ";
+	break;
     default:
 	sprintf(smbuf, " model 0x%x", hwid & 0xff);
 	submodel = smbuf;
diff --git a/sys/dev/mlx/mlx_disk.c b/sys/dev/mlx/mlx_disk.c
index 85f8314cb67..9e2f571e406 100644
--- a/sys/dev/mlx/mlx_disk.c
+++ b/sys/dev/mlx/mlx_disk.c
@@ -104,19 +104,10 @@ static driver_t mlxd_driver = {
 
 DRIVER_MODULE(mlxd, mlx, mlxd_driver, mlxd_devclass, 0, 0);
 
-static __inline struct mlxd_softc *
-mlxd_getsoftc(dev_t dev)
-{
-    int unit;
-
-    unit = dkunit(dev);
-    return ((struct mlxd_softc *)devclass_get_softc(mlxd_devclass, unit));
-}
-
 static int
 mlxd_open(dev_t dev, int flags, int fmt, struct proc *p)
 {
-    struct mlxd_softc	*sc = mlxd_getsoftc(dev);
+    struct mlxd_softc	*sc = (struct mlxd_softc *)dev->si_drv1;
     struct disklabel	*label;
 
     debug("called");
@@ -138,9 +129,6 @@ mlxd_open(dev_t dev, int flags, int fmt, struct proc *p)
     label->d_secpercyl  = sc->mlxd_drive->ms_sectors * sc->mlxd_drive->ms_heads;
     label->d_secperunit = sc->mlxd_drive->ms_size;
 
-    /* set maximum I/O size */
-    dev->si_iosize_max = sc->mlxd_controller->mlx_maxiosize;
-	
     sc->mlxd_flags |= MLXD_OPEN;
     return (0);
 }
@@ -148,7 +136,7 @@ mlxd_open(dev_t dev, int flags, int fmt, struct proc *p)
 static int
 mlxd_close(dev_t dev, int flags, int fmt, struct proc *p)
 {
-    struct mlxd_softc *sc = mlxd_getsoftc(dev);
+    struct mlxd_softc	*sc = (struct mlxd_softc *)dev->si_drv1;
 
     debug("called");
 	
@@ -161,7 +149,7 @@ mlxd_close(dev_t dev, int flags, int fmt, struct proc *p)
 static int
 mlxd_ioctl(dev_t dev, u_long cmd, caddr_t addr, int32_t flag, struct proc *p)
 {
-    struct mlxd_softc *sc = mlxd_getsoftc(dev);
+    struct mlxd_softc	*sc = (struct mlxd_softc *)dev->si_drv1;
     int error;
 
     debug("called");
@@ -185,7 +173,7 @@ mlxd_ioctl(dev_t dev, u_long cmd, caddr_t addr, int32_t flag, struct proc *p)
 static void
 mlxd_strategy(struct buf *bp)
 {
-    struct mlxd_softc	*sc = mlxd_getsoftc(bp->b_dev);
+    struct mlxd_softc	*sc = (struct mlxd_softc *)bp->b_dev->si_drv1;
     int			s;
 
     debug("called");
@@ -206,8 +194,6 @@ mlxd_strategy(struct buf *bp)
     if (bp->b_bcount == 0)
 	goto done;
 
-    /* pass reference to us */
-    bp->b_driver1 = sc;
     s = splbio();
     devstat_start_transaction(&sc->mlxd_stats);
     mlx_submit_buf(sc->mlxd_controller, bp);
@@ -230,7 +216,7 @@ void
 mlxd_intr(void *data)
 {
     struct buf *bp = (struct buf *)data;
-    struct mlxd_softc *sc = (struct mlxd_softc *)bp->b_driver1;
+    struct mlxd_softc	*sc = (struct mlxd_softc *)bp->b_dev->si_drv1;
 
     debug("called");
 	
@@ -259,6 +245,7 @@ mlxd_attach(device_t dev)
     struct mlxd_softc	*sc = (struct mlxd_softc *)device_get_softc(dev);
     device_t		parent;
     char		*state;
+    dev_t		dsk;
     
     debug("called");
 
@@ -290,9 +277,13 @@ mlxd_attach(device_t dev)
 		      DEVSTAT_TYPE_DIRECT | DEVSTAT_TYPE_IF_OTHER, 
 		      DEVSTAT_PRIORITY_DA);
 
-    disk_create(sc->mlxd_unit, &sc->mlxd_disk, 0, &mlxd_cdevsw, &mlxddisk_cdevsw);
+    dsk = disk_create(sc->mlxd_unit, &sc->mlxd_disk, 0, &mlxd_cdevsw, &mlxddisk_cdevsw);
     disks_registered++;
 
+    /* set maximum I/O size */
+    dsk->si_iosize_max = sc->mlxd_controller->mlx_maxiosize * MLX_BLKSIZE;
+    dsk->si_drv1 = sc;
+
     return (0);
 }
 
diff --git a/sys/dev/mlx/mlx_pci.c b/sys/dev/mlx/mlx_pci.c
index 7d791a8423b..8aa9e1a0032 100644
--- a/sys/dev/mlx/mlx_pci.c
+++ b/sys/dev/mlx/mlx_pci.c
@@ -88,6 +88,7 @@ struct
     char	*desc;
 } mlx_identifiers[] = {
     {0x1069, 0x0002, MLX_IFTYPE_3, "Mylex version 3 RAID interface"},	/* Mylex v3 software interface */
+    {0x1069, 0x0010, MLX_IFTYPE_4, "Mylex version 4 RAID interface"},	/* Mylex v4 software interface */
     {0, 0, 0, 0}
 };
 
diff --git a/sys/dev/mlx/mlxreg.h b/sys/dev/mlx/mlxreg.h
index 713022334df..e287067c7cb 100644
--- a/sys/dev/mlx/mlxreg.h
+++ b/sys/dev/mlx/mlxreg.h
@@ -50,6 +50,65 @@
 #define MLX_STATUS_WEDGED	0xdead	/* controller not listening */
 #define MLX_STATUS_BUSY		0xffff	/* command is in controller */
 
+/*
+ * Accessor defines for the V3 interface.
+ */
+#define MLX_V3_MAILBOX		0x00
+#define	MLX_V3_STATUS_IDENT	0x0d
+#define MLX_V3_STATUS		0x0e
+#define MLX_V3_IDBR		0x40
+#define MLX_V3_ODBR		0x41
+#define MLX_V3_IER		0x43
+
+#define MLX_V3_PUT_MAILBOX(sc, idx, val) bus_space_write_1(sc->mlx_btag, sc->mlx_bhandle, MLX_V3_MAILBOX + idx, val)
+#define MLX_V3_GET_STATUS_IDENT(sc)	 bus_space_read_1 (sc->mlx_btag, sc->mlx_bhandle, MLX_V3_STATUS_IDENT)
+#define MLX_V3_GET_STATUS(sc)		 bus_space_read_2 (sc->mlx_btag, sc->mlx_bhandle, MLX_V3_STATUS)
+#define MLX_V3_GET_IDBR(sc)		 bus_space_read_1 (sc->mlx_btag, sc->mlx_bhandle, MLX_V3_IDBR)
+#define MLX_V3_PUT_IDBR(sc, val)	 bus_space_write_1(sc->mlx_btag, sc->mlx_bhandle, MLX_V3_IDBR, val)
+#define MLX_V3_GET_ODBR(sc)		 bus_space_read_1 (sc->mlx_btag, sc->mlx_bhandle, MLX_V3_ODBR)
+#define MLX_V3_PUT_ODBR(sc, val)	 bus_space_write_1(sc->mlx_btag, sc->mlx_bhandle, MLX_V3_ODBR, val)
+#define MLX_V3_PUT_IER(sc, val)		 bus_space_write_1(sc->mlx_btag, sc->mlx_bhandle, MLX_V3_IER, val)
+
+#define MLX_V3_IDB_FULL		(1<<0)		/* mailbox is full */
+#define MLX_V3_IDB_SACK		(1<<1)		/* acknowledge status read */
+
+#define MLX_V3_ODB_SAVAIL	(1<<0)		/* status is available */
+
+/*
+ * Accessor defines for the V4 interface.
+ */
+#define MLX_V4_MAILBOX		0x1000
+#define	MLX_V4_STATUS_IDENT	0x1018
+#define MLX_V4_STATUS		0x101a
+#define MLX_V4_IDBR		0x0020
+#define MLX_V4_ODBR		0x002c
+#define MLX_V4_IER		0x0034
+
+/* use longword access? */
+#define MLX_V4_PUT_MAILBOX(sc, idx, val) bus_space_write_1(sc->mlx_btag, sc->mlx_bhandle, MLX_V4_MAILBOX + idx, val)
+#define MLX_V4_GET_STATUS_IDENT(sc)	 bus_space_read_1 (sc->mlx_btag, sc->mlx_bhandle, MLX_V4_STATUS_IDENT)
+#define MLX_V4_GET_STATUS(sc)		 bus_space_read_2 (sc->mlx_btag, sc->mlx_bhandle, MLX_V4_STATUS)
+#define MLX_V4_GET_IDBR(sc)		 bus_space_read_4 (sc->mlx_btag, sc->mlx_bhandle, MLX_V4_IDBR)
+#define MLX_V4_PUT_IDBR(sc, val)	 bus_space_write_4(sc->mlx_btag, sc->mlx_bhandle, MLX_V4_IDBR, val)
+#define MLX_V4_GET_ODBR(sc)		 bus_space_read_4 (sc->mlx_btag, sc->mlx_bhandle, MLX_V4_ODBR)
+#define MLX_V4_PUT_ODBR(sc, val)	 bus_space_write_4(sc->mlx_btag, sc->mlx_bhandle, MLX_V4_ODBR, val)
+#define MLX_V4_PUT_IER(sc, val)		 bus_space_write_4(sc->mlx_btag, sc->mlx_bhandle, MLX_V4_IER, val)
+
+#define MLX_V4_IDB_FULL		(1<<0)		/* mailbox is full */
+
+#define MLX_V4_IDB_HWMBOX_CMD	(1<<0)		/* posted hardware mailbox command */
+#define MLX_V4_IDB_SACK		(1<<1)		/* acknowledge status read */
+#define MLX_V4_IDB_MEMMBOX_CMD	(1<<4)		/* posted memory mailbox command */
+
+#define MLX_V4_ODB_HWSAVAIL	(1<<0)		/* status is available for hardware mailbox */
+#define MLX_V4_ODB_MEMSAVAIL	(1<<1)		/* status is available for memory mailbox */
+
+#define MLX_V4_ODB_HWMBOX_ACK	(1<<0)		/* ack status read from hardware mailbox */
+#define MLX_V4_ODB_MEMMBOX_ACK	(1<<1)		/* ack status read from memory mailbox */
+
+#define MLX_V4_IER_MASK		0xfb		/* message unit interrupt mask */
+#define MLX_V4_IER_DISINT	(1<<2)		/* interrupt disable bit */
+
 /*
  * Scatter-gather list format, type 1, kind 00.
  */
diff --git a/sys/dev/mlx/mlxvar.h b/sys/dev/mlx/mlxvar.h
index 7679dbbce9b..ec69b25eebc 100644
--- a/sys/dev/mlx/mlxvar.h
+++ b/sys/dev/mlx/mlxvar.h
@@ -159,8 +159,6 @@ struct mlx_softc
     void		(* mlx_intaction)(struct mlx_softc *sc, int action);
 #define MLX_INTACTION_DISABLE		0
 #define MLX_INTACTION_ENABLE		1
-#define MLX_INTACTION_ACKNOWLEDGE	2
-
 };
 
 /*
@@ -204,31 +202,6 @@ extern int	mlx_submit_ioctl(struct mlx_softc *sc, struct mlx_sysdrive *drive, u_
 				 caddr_t addr, int32_t flag, struct proc *p);
 extern void	mlxd_intr(void *data);
 
-/*
- * Accessor defines for the V3 interface.
- */
-#define MLX_V3_MAILBOX		0x00
-#define	MLX_V3_STATUS_IDENT	0x0d
-#define MLX_V3_STATUS		0x0e
-#define MLX_V3_IDBR		0x40
-#define MLX_V3_ODBR		0x41
-#define MLX_V3_IER		0x43
-
-#define MLX_V3_PUT_MAILBOX(sc, idx, val) bus_space_write_1(sc->mlx_btag, sc->mlx_bhandle, MLX_V3_MAILBOX + idx, val)
-#define MLX_V3_GET_STATUS_IDENT(sc)	 bus_space_read_1 (sc->mlx_btag, sc->mlx_bhandle, MLX_V3_STATUS_IDENT)
-#define MLX_V3_GET_STATUS(sc)		 bus_space_read_2 (sc->mlx_btag, sc->mlx_bhandle, MLX_V3_STATUS)
-#define MLX_V3_GET_IDBR(sc)		 bus_space_read_1 (sc->mlx_btag, sc->mlx_bhandle, MLX_V3_IDBR)
-#define MLX_V3_PUT_IDBR(sc, val)	 bus_space_write_1(sc->mlx_btag, sc->mlx_bhandle, MLX_V3_IDBR, val)
-#define MLX_V3_GET_ODBR(sc)		 bus_space_read_1 (sc->mlx_btag, sc->mlx_bhandle, MLX_V3_ODBR)
-#define MLX_V3_PUT_ODBR(sc, val)	 bus_space_write_1(sc->mlx_btag, sc->mlx_bhandle, MLX_V3_ODBR, val)
-#define MLX_V3_PUT_IER(sc, val)		 bus_space_write_1(sc->mlx_btag, sc->mlx_bhandle, MLX_V3_IER, val)
-
-#define MLX_V3_IDB_FULL		(1<<0)		/* mailbox is full */
-#define MLX_V3_IDB_SACK		(1<<1)		/* acknowledge status read */
-#define MLX_V3_IDB_RESET	(1<<3)		/* request soft reset */
-
-#define MLX_V3_ODB_SAVAIL	(1<<0)		/* status is available */
-
 /*
  * Inlines to build various command structures
  */