diff --git a/sys/arch/pmax/dev/dc.c b/sys/arch/pmax/dev/dc.c
index 05c8065f1fdd..13557c42b425 100644
--- a/sys/arch/pmax/dev/dc.c
+++ b/sys/arch/pmax/dev/dc.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: dc.c,v 1.21 1996/09/02 06:44:00 mycroft Exp $	*/
+/*	$NetBSD: dc.c,v 1.22 1996/09/11 06:41:19 jonathan Exp $	*/
 
 /*-
  * Copyright (c) 1992, 1993
@@ -35,7 +35,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	@(#)dc.c	8.2 (Berkeley) 11/30/93
+ *	@(#)dc.c	8.5 (Berkeley) 6/2/95
  */
 
 /*
@@ -421,7 +421,10 @@ dcopen(dev, flag, mode, p)
 		ttsetwater(tp);
 	} else if ((tp->t_state & TS_XCLUDE) && curproc->p_ucred->cr_uid != 0)
 		return (EBUSY);
-	(void) dcmctl(dev, DML_DTR, DMSET);
+	(void) dcmctl(dev, DML_DTR | DML_RTS, DMSET);
+	if ((dcsoftCAR[unit >> 2] & (1 << (unit & 03))) ||
+	    (dcmctl(dev, 0, DMGET) & DML_CAR))
+		tp->t_state |= TS_CARR_ON;
 	s = spltty();
 	while (!(flag & O_NONBLOCK) && !(tp->t_cflag & CLOCAL) &&
 	       !(tp->t_state & TS_CARR_ON)) {
@@ -445,14 +448,18 @@ dcclose(dev, flag, mode, p)
 {
 	register struct tty *tp;
 	register int unit, bit;
+	int s;
 
 	unit = minor(dev);
 	tp = dc_tty[unit];
 	bit = 1 << ((unit & 03) + 8);
+	s = spltty();
+	/* turn off the break bit if it is set */
 	if (dc_brk[unit >> 2] & bit) {
 		dc_brk[unit >> 2] &= ~bit;
 		ttyoutput(0, tp);
 	}
+	splx(s);
 	(*linesw[tp->t_line].l_close)(tp, flag);
 	if ((tp->t_cflag & HUPCL) || (tp->t_state & TS_WOPEN) ||
 	    !(tp->t_state & TS_ISOPEN))
@@ -468,6 +475,11 @@ dcread(dev, uio, flag)
 	register struct tty *tp;
 
 	tp = dc_tty[minor(dev)];
+	if ((tp->t_cflag & CRTS_IFLOW) && (tp->t_state & TS_TBLOCK) &&
+	    tp->t_rawq.c_cc < TTYHOG/5) {
+		tp->t_state &= ~TS_TBLOCK;
+		(void) dcmctl(dev, DML_RTS, DMBIS);
+	}
 	return ((*linesw[tp->t_line].l_read)(tp, uio, flag));
 }
 
@@ -564,6 +576,7 @@ dcparam(tp, t)
 	register int cflag = t->c_cflag;
 	int unit = minor(tp->t_dev);
 	int ospeed = ttspeedtab(t->c_ospeed, dcspeedtab);
+	int s;
 
 	/* check requested parameters */
         if (ospeed < 0 || (t->c_ispeed && t->c_ispeed != t->c_ospeed) ||
@@ -575,28 +588,22 @@ dcparam(tp, t)
         tp->t_ospeed = t->c_ospeed;
         tp->t_cflag = cflag;
 
-	dcaddr = (dcregs *)dcpdma[unit].p_addr;
-
 	/*
 	 * Handle console cases specially.
 	 */
 	if (raster_console()) {
 		if (unit == DCKBD_PORT) {
-			dcaddr->dc_lpr = LPR_RXENAB | LPR_8_BIT_CHAR |
+			lpr = LPR_RXENAB | LPR_8_BIT_CHAR |
 				LPR_B4800 | DCKBD_PORT;
-			wbflush();
-			return (0);
+			goto out;
 		} else if (unit == DCMOUSE_PORT) {
-			dcaddr->dc_lpr = LPR_RXENAB | LPR_B4800 | LPR_OPAR |
+			lpr = LPR_RXENAB | LPR_B4800 | LPR_OPAR |
 				LPR_PARENB | LPR_8_BIT_CHAR | DCMOUSE_PORT;
-			wbflush();
-			return (0);
+			goto out;
 		}
 	} else if (tp->t_dev == cn_tab->cn_dev) {
-		dcaddr->dc_lpr = LPR_RXENAB | LPR_8_BIT_CHAR |
-			LPR_B9600 | unit;
-		wbflush();
-		return (0);
+		lpr = LPR_RXENAB | LPR_8_BIT_CHAR | LPR_B9600 | unit;
+		goto out;
 	}
 	if (ospeed == 0) {
 		(void) dcmctl(unit, 0, DMSET);	/* hang up line */
@@ -613,8 +620,12 @@ dcparam(tp, t)
 		lpr |= LPR_OPAR;
 	if (cflag & CSTOPB)
 		lpr |= LPR_2_STOP;
+out:
+	dcaddr = (dcregs *)dcpdma[unit].p_addr;
+	s = spltty();
 	dcaddr->dc_lpr = lpr;
 	wbflush();
+	splx(s);
 	DELAY(10);
 	return (0);
 }
@@ -695,6 +706,11 @@ dcrint(unit)
 			cc |= TTY_FE;
 		if (c & RBUF_PERR)
 			cc |= TTY_PE;
+		if ((tp->t_cflag & CRTS_IFLOW) && !(tp->t_state & TS_TBLOCK) &&
+		    tp->t_rawq.c_cc + tp->t_canq.c_cc >= TTYHOG) {
+			tp->t_state &= ~TS_TBLOCK;
+			(void) dcmctl(tp->t_dev, DML_RTS, DMBIC);
+		}
 		(*linesw[tp->t_line].l_rint)(cc, tp);
 	}
 	DELAY(10);
@@ -706,12 +722,38 @@ dcxint(tp)
 {
 	register struct pdma *dp;
 	register dcregs *dcaddr;
-	int unit = minor(tp->t_dev);
+	int unit;
 
+	unit = minor(tp->t_dev);
 	dp = &dcpdma[unit];
 	if (dp->p_mem < dp->p_end) {
 		dcaddr = (dcregs *)dp->p_addr;
-		dcaddr->dc_tdr = dc_brk[unit >> 2] | *dp->p_mem++; 
+		/* check for hardware flow control of output */
+		if ((tp->t_cflag & CCTS_OFLOW) && pmax_boardtype != DS_PMAX) {
+			switch (unit) {
+			case DCCOMM_PORT:
+				if (dcaddr->dc_msr & MSR_CTS2)
+					break;
+				goto stop;
+
+			case DCPRINTER_PORT:
+				if (dcaddr->dc_msr & MSR_CTS3)
+					break;
+			stop:
+				tp->t_state &= ~TS_BUSY;
+				tp->t_state |= TS_TTSTOP;
+				ndflush(&tp->t_outq, dp->p_mem - 
+						(caddr_t)tp->t_outq.c_cf);
+				dp->p_end = dp->p_mem = tp->t_outq.c_cf;
+				dcaddr->dc_tcr &= ~(1 << unit);
+				wbflush();
+				DELAY(10);
+				return;
+			}
+		}
+		dcaddr->dc_tdr = dc_brk[unit >> 2] | *(u_char *)dp->p_mem;
+		dp->p_mem++;
+
 		wbflush();
 		DELAY(10);
 		return;
@@ -742,9 +784,9 @@ dcstart(tp)
 	register struct pdma *dp;
 	register dcregs *dcaddr;
 	register int cc;
-	int s;
+	int unit, s;
 
-	dp = &dcpdma[minor(tp->t_dev)];
+	dp = &dcpdma[unit = minor(tp->t_dev)];
 	dcaddr = (dcregs *)dp->p_addr;
 	s = spltty();
 	if (tp->t_state & (TS_TIMEOUT|TS_BUSY|TS_TTSTOP))
@@ -777,14 +819,11 @@ dcstart(tp)
 		}
 		goto out;
 	}
-	cc = ndqb(&tp->t_outq, 0);
-	if (cc == 0) 
-		goto out;
-
+  	cc = ndqb(&tp->t_outq, 0);
 	tp->t_state |= TS_BUSY;
 	dp->p_end = dp->p_mem = tp->t_outq.c_cf;
 	dp->p_end += cc;
-	dcaddr->dc_tcr |= 1 << (minor(tp->t_dev) & 03);
+	dcaddr->dc_tcr |= 1 << (unit & 03);
 	wbflush();
 out:
 	splx(s);
@@ -819,19 +858,22 @@ dcmctl(dev, bits, how)
 	register dcregs *dcaddr;
 	register int unit, mbits;
 	int b, s;
-	register int msr;
+	register int tcr, msr;
 
 	unit = minor(dev);
 	b = 1 << (unit & 03);
 	dcaddr = (dcregs *)dcpdma[unit].p_addr;
 	s = spltty();
-	/* only channel 2 has modem control (what about line 3?) */
-	mbits = DML_DTR | DML_DSR | DML_CAR;
+	/* only channel 2 has modem control on a DECstation 2100/3100 */
+	mbits = DML_DTR | DML_RTS | DML_DSR | DML_CAR;
 	switch (unit & 03) {
 	case 2:
 		mbits = 0;
-		if (dcaddr->dc_tcr & TCR_DTR2)
+		tcr = dcaddr->dc_tcr;
+		if (tcr & TCR_DTR2)
 			mbits |= DML_DTR;
+		if (pmax_boardtype != DS_PMAX && (tcr & TCR_RTS2))
+			mbits |= DML_RTS;
 		msr = dcaddr->dc_msr;
 		if (msr & MSR_CD2)
 			mbits |= DML_CAR;
@@ -846,8 +888,11 @@ dcmctl(dev, bits, how)
 	case 3:
 		if (pmax_boardtype != DS_PMAX) {
 			mbits = 0;
-			if (dcaddr->dc_tcr & TCR_DTR3)
+			tcr = dcaddr->dc_tcr;
+			if (tcr & TCR_DTR3)
 				mbits |= DML_DTR;
+			if (tcr & TCR_RTS3)
+				mbits |= DML_RTS;
 			msr = dcaddr->dc_msr;
 			if (msr & MSR_CD3)
 				mbits |= DML_CAR;
@@ -874,22 +919,34 @@ dcmctl(dev, bits, how)
 	}
 	switch (unit & 03) {
 	case 2:
+		tcr = dcaddr->dc_tcr;
 		if (mbits & DML_DTR)
-			dcaddr->dc_tcr |= TCR_DTR2;
+			tcr |= TCR_DTR2;
 		else
-			dcaddr->dc_tcr &= ~TCR_DTR2;
+			tcr &= ~TCR_DTR2;
+		if (pmax_boardtype != DS_PMAX) {
+			if (mbits & DML_RTS)
+				tcr |= TCR_RTS2;
+			else
+				tcr &= ~TCR_RTS2;
+		}
+		dcaddr->dc_tcr = tcr;
 		break;
 
 	case 3:
 		if (pmax_boardtype != DS_PMAX) {
+			tcr = dcaddr->dc_tcr;
 			if (mbits & DML_DTR)
-				dcaddr->dc_tcr |= TCR_DTR3;
+				tcr |= TCR_DTR3;
 			else
-				dcaddr->dc_tcr &= ~TCR_DTR3;
+				tcr &= ~TCR_DTR3;
+			if (mbits & DML_RTS)
+				tcr |= TCR_RTS3;
+			else
+				tcr &= ~TCR_RTS3;
+			dcaddr->dc_tcr = tcr;
 		}
 	}
-	if ((mbits & DML_DTR) && (dcsoftCAR[unit >> 2] & b))
-		dc_tty[unit]->t_state |= TS_CARR_ON;
 	(void) splx(s);
 	return (mbits);
 }
@@ -904,25 +961,45 @@ dcscan(arg)
 {
 	register dcregs *dcaddr;
 	register struct tty *tp;
-	register int i, bit, car;
+	register int unit, limit, dtr, dsr;
 	int s;
 
+	/* only channel 2 has modem control on a DECstation 2100/3100 */
+	dtr = TCR_DTR2;
+	dsr = MSR_DSR2;
+	limit = (pmax_boardtype == DS_PMAX) ? 2 : 3;
 	s = spltty();
-	/* only channel 2 has modem control (what about line 3?) */
-	dcaddr = (dcregs *)dcpdma[i = 2].p_addr;
-	tp = dc_tty[i];
-	bit = TCR_DTR2;
-	if (dcsoftCAR[i >> 2] & bit)
-		car = 1;
-	else
-		car = dcaddr->dc_msr & MSR_DSR2;
-	if (car) {
-		/* carrier present */
-		if (!(tp->t_state & TS_CARR_ON))
-			(void)(*linesw[tp->t_line].l_modem)(tp, 1);
-	} else if ((tp->t_state & TS_CARR_ON) &&
-	    (*linesw[tp->t_line].l_modem)(tp, 0) == 0)
-		dcaddr->dc_tcr &= ~bit;
+	for (unit = 2; unit <= limit; unit++, dtr >>= 2, dsr >>= 8) {
+		tp = dc_tty[unit];
+		dcaddr = (dcregs *)dcpdma[unit].p_addr;
+		if ((dcaddr->dc_msr & dsr) || (dcsoftCAR[0] & (1 << unit))) {
+			/* carrier present */
+			if (!(tp->t_state & TS_CARR_ON))
+				(void)(*linesw[tp->t_line].l_modem)(tp, 1);
+		} else if ((tp->t_state & TS_CARR_ON) &&
+		    (*linesw[tp->t_line].l_modem)(tp, 0) == 0)
+			dcaddr->dc_tcr &= ~dtr;
+		/*
+		 * If we are using hardware flow control and output is stopped,
+		 * then resume transmit.
+		 */
+		if ((tp->t_cflag & CCTS_OFLOW) && (tp->t_state & TS_TTSTOP) &&
+		    pmax_boardtype != DS_PMAX) {
+			switch (unit) {
+			case DCCOMM_PORT:
+				if (dcaddr->dc_msr & MSR_CTS2)
+					break;
+				continue;
+
+			case DCPRINTER_PORT:
+				if (dcaddr->dc_msr & MSR_CTS3)
+					break;
+				continue;
+			}
+			tp->t_state &= ~TS_TTSTOP;
+			dcstart(tp);
+		}
+	}
 	splx(s);
 	timeout(dcscan, (void *)0, hz);
 }