diff -uF^[a-zA-Z_][a-z 	A-Z0-9_]*(.*[^;]$ arch/alpha/tc/scc.c.orig arch/alpha/tc/scc.c
--- arch/alpha/tc/scc.c.orig	Wed Sep  3 23:41:34 1997
+++ arch/alpha/tc/scc.c	Tue Mar 10 23:07:43 1998
@@ -228,6 +228,9 @@ static void	rr __P((char *, scc_regmap_t
 static void	scc_modem_intr __P((dev_t));
 static void	sccreset __P((struct scc_softc *));
 
+static void	scc_txintr __P((struct scc_softc *, int, scc_regmap_t *));
+static void	scc_rxintr __P((struct scc_softc *, int, scc_regmap_t *, int));
+static void	scc_stintr __P((struct scc_softc *, int, scc_regmap_t *, int));
 int	sccintr __P((void *));
 void	scc_alphaintr __P((int));
 
@@ -969,144 +972,185 @@ cold_sccparam(tp, t, sc)
 }
 
 
-/*
- * Check for interrupts from all devices.
- */
-int
-sccintr(xxxsc)
-	void *xxxsc;
+/* transmission done interrupts */
+static void
+scc_txintr(sc, chan, regs)
+	struct scc_softc *sc;
+	int chan;
+	scc_regmap_t *regs;
 {
-	register struct scc_softc *sc = (struct scc_softc *)xxxsc;
-	register int unit = (long)sc->sc_dv.dv_unit;
-	register scc_regmap_t *regs;
-	register struct tty *tp;
-	register struct pdma *dp;
-	register int cc, chan, rr1, rr2, rr3;
-	int overrun = 0;
-
-	rr1 = 0;		/* shut up gcc -Wall */
-	regs = (scc_regmap_t *)sc->scc_pdma[0].p_addr;
-	unit <<= 1;
-	for (;;) {
-	    SCC_READ_REG(regs, SCC_CHANNEL_B, ZSRR_IVEC, rr2);
-	    rr2 = SCC_RR2_STATUS(rr2);
-	    /* are we done yet ? */
-	    if (rr2 == 6) {	/* strange, distinguished value */
-		SCC_READ_REG(regs, SCC_CHANNEL_A, ZSRR_IPEND, rr3);
-		if (rr3 == 0)
-			return 1;
-	    }
+	register struct tty *tp = sc->scc_tty[chan];
+	register struct pdma *dp = &sc->scc_pdma[chan];
+	register int cc;
 
-	    SCC_WRITE_REG(regs, SCC_CHANNEL_A, SCC_RR0, ZSWR0_CLR_INTR);
-	    if ((rr2 == SCC_RR2_A_XMIT_DONE) || (rr2 == SCC_RR2_B_XMIT_DONE)) {
-		chan = (rr2 == SCC_RR2_A_XMIT_DONE) ?
-			SCC_CHANNEL_A : SCC_CHANNEL_B;
-		tp = sc->scc_tty[chan];
-		dp = &sc->scc_pdma[chan];
-		if (dp->p_mem < dp->p_end) {
-			SCC_WRITE_DATA(regs, chan, *dp->p_mem++);
+	tp = sc->scc_tty[chan];
+	dp = &sc->scc_pdma[chan];
+	if (dp->p_mem < dp->p_end) {
+		SCC_WRITE_DATA(regs, chan, *dp->p_mem++);
 #ifdef pmax	/* Alpha handles the 1.6 msec settle time in hardware */
-			DELAY(2);
+		DELAY(2);
 #endif
+		tc_mb();
+	} else {
+		tp->t_state &= ~TS_BUSY;
+		if (tp->t_state & TS_FLUSH)
+			tp->t_state &= ~TS_FLUSH;
+		else {
+			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;
+		}
+		if (tp->t_line)
+			(*linesw[tp->t_line].l_start)(tp);
+		else
+			sccstart(tp);
+		if (tp->t_outq.c_cc == 0 || !(tp->t_state & TS_BUSY)) {
+			SCC_READ_REG(regs, chan, SCC_RR15, cc);
+			cc &= ~ZSWR15_TXUEOM_IE;
+			SCC_WRITE_REG(regs, chan, SCC_WR15, cc);
+			cc = sc->scc_wreg[chan].wr1 & ~ZSWR1_TIE;
+			SCC_WRITE_REG(regs, chan, SCC_WR1, cc);
+			sc->scc_wreg[chan].wr1 = cc;
 			tc_mb();
-		} else {
-			tp->t_state &= ~TS_BUSY;
-			if (tp->t_state & TS_FLUSH)
-				tp->t_state &= ~TS_FLUSH;
-			else {
-				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;
-			}
-			if (tp->t_line)
-				(*linesw[tp->t_line].l_start)(tp);
-			else
-				sccstart(tp);
-			if (tp->t_outq.c_cc == 0 || !(tp->t_state & TS_BUSY)) {
-				SCC_READ_REG(regs, chan, SCC_RR15, cc);
-				cc &= ~ZSWR15_TXUEOM_IE;
-				SCC_WRITE_REG(regs, chan, SCC_WR15, cc);
-				cc = sc->scc_wreg[chan].wr1 & ~ZSWR1_TIE;
-				SCC_WRITE_REG(regs, chan, SCC_WR1, cc);
-				sc->scc_wreg[chan].wr1 = cc;
-				tc_mb();
-			}
 		}
-	    } else if (rr2 == SCC_RR2_A_RECV_DONE ||
-		rr2 == SCC_RR2_B_RECV_DONE || rr2 == SCC_RR2_A_RECV_SPECIAL ||
+	}
+}
+
+/* receive interrupts */
+static void
+scc_rxintr(sc, chan, regs, unit)
+	struct scc_softc *sc;
+	int chan;
+	scc_regmap_t *regs;
+	int unit;
+{
+	register struct tty *tp = sc->scc_tty[chan];
+	int cc, rr1 = 0, rr2 = 0;	/* XXX */
+
+	SCC_READ_DATA(regs, chan, cc);
+	if (rr2 == SCC_RR2_A_RECV_SPECIAL ||
 		rr2 == SCC_RR2_B_RECV_SPECIAL) {
-		if (rr2 == SCC_RR2_A_RECV_DONE || rr2 == SCC_RR2_A_RECV_SPECIAL)
-			chan = SCC_CHANNEL_A;
-		else
-			chan = SCC_CHANNEL_B;
-		tp = sc->scc_tty[chan];
-		SCC_READ_DATA(regs, chan, cc);
-		if (rr2 == SCC_RR2_A_RECV_SPECIAL ||
-			rr2 == SCC_RR2_B_RECV_SPECIAL) {
-			SCC_READ_REG(regs, chan, SCC_RR1, rr1);
-			SCC_WRITE_REG(regs, chan, SCC_RR0, ZSWR0_RESET_ERRORS);
-			if ((rr1 & ZSRR1_DO) && overrun == 0) {
-				log(LOG_WARNING, "scc%d,%d: silo overflow\n",
-					unit >> 1, chan);
-				overrun = 1;
-			}
+		SCC_READ_REG(regs, chan, SCC_RR1, rr1);
+		SCC_WRITE_REG(regs, chan, SCC_RR0, ZSWR0_RESET_ERRORS);
+		if (rr1 & ZSRR1_DO) {
+			log(LOG_WARNING, "scc%d,%d: silo overflow\n",
+				unit >> 1, chan);
 		}
+	}
 
-		/*
-		 * Keyboard needs special treatment.
-		 */
-		if (tp == scctty(makedev(SCCDEV, SCCKBD_PORT)) /* && cn_tab.cn_screen */) {
+	/*
+	 * Keyboard needs special treatment.
+	 */
+	if (tp == scctty(makedev(SCCDEV, SCCKBD_PORT)) /* && cn_tab.cn_screen */) {
 #ifdef KADB
-			if (cc == LK_DO) {
-				spl0();
-				kdbpanic();
-				return;
-			}
+		if (cc == LK_DO) {
+			spl0();
+			kdbpanic();
+			return;		/* XXXXXXXXXXX ??? true return */
+		}
 #endif
 #ifdef DEBUG
-			debugChar = cc;
+		debugChar = cc;
 #endif
-			if (sccDivertXInput) {
-				(*sccDivertXInput)(cc);
-				continue;
-			}
+		if (sccDivertXInput) {
+			(*sccDivertXInput)(cc);
+			return;
+		}
 #ifdef TK_NOTYET
-			if ((cc = kbdMapChar(cc)) < 0)
-				continue;
+		if ((cc = kbdMapChar(cc)) < 0)
+			return;
 #endif
-		/*
-		 * Now for mousey
-		 */
-		} else if (tp == scctty(makedev(SCCDEV, SCCMOUSE_PORT)) &&
-		    sccMouseButtons) {
+	/*
+	 * Now for mousey
+	 */
+	} else if (tp == scctty(makedev(SCCDEV, SCCMOUSE_PORT)) &&
+	    sccMouseButtons) {
 #ifdef HAVE_RCONS
-			/*XXX*/
-			mouseInput(cc);
+		/*XXX*/
+		mouseInput(cc);
 #endif
-			continue;
-		}
-		if (!(tp->t_state & TS_ISOPEN)) {
-			wakeup((caddr_t)&tp->t_rawq);
+		return;
+	}
+	if (!(tp->t_state & TS_ISOPEN)) {
+		wakeup((caddr_t)&tp->t_rawq);
 #ifdef PORTSELECTOR
-			if (!(tp->t_state & TS_WOPEN))
+		if (!(tp->t_state & TS_WOPEN))
 #endif
-				continue;
-		}
-		if (rr2 == SCC_RR2_A_RECV_SPECIAL ||
-			rr2 == SCC_RR2_B_RECV_SPECIAL) {
-			if (rr1 & ZSRR1_PE)
-				cc |= TTY_PE;
-			if (rr1 & ZSRR1_FE)
-				cc |= TTY_FE;
-		}
-		(*linesw[tp->t_line].l_rint)(cc, tp);
-	    } else if ((rr2 == SCC_RR2_A_EXT_STATUS) || (rr2 == SCC_RR2_B_EXT_STATUS)) {
-		chan = (rr2 == SCC_RR2_A_EXT_STATUS) ?
-		    SCC_CHANNEL_A : SCC_CHANNEL_B;
-		SCC_WRITE_REG(regs, chan, SCC_RR0, ZSWR0_RESET_STATUS);
-		scc_modem_intr(unit | chan);
-	    }
+			return;
+	}
+	if (rr2 == SCC_RR2_A_RECV_SPECIAL ||
+		rr2 == SCC_RR2_B_RECV_SPECIAL) {
+		if (rr1 & ZSRR1_PE)
+			cc |= TTY_PE;
+		if (rr1 & ZSRR1_FE)
+			cc |= TTY_FE;
+	}
+	(*linesw[tp->t_line].l_rint)(cc, tp);
+}
+
+/* status interrupts */
+static void
+scc_stintr(sc, chan, regs, unit)
+	struct scc_softc *sc;
+	int chan;
+	scc_regmap_t *regs;
+	int unit;
+{
+
+	SCC_WRITE_REG(regs, chan, SCC_RR0, ZSWR0_RESET_STATUS);
+	scc_modem_intr(unit | chan);
+}
+
+/*
+ * Check for interrupts from all devices.
+ */
+int
+sccintr(xxxsc)
+	void *xxxsc;
+{
+	register struct scc_softc *sc = (struct scc_softc *)xxxsc;
+	register int unit = (long)sc->sc_dv.dv_unit;
+	register scc_regmap_t *regs;
+	register int rr3;
+
+	regs = (scc_regmap_t *)sc->scc_pdma[0].p_addr;
+	unit <<= 1;
+
+	/* Note: only channel A has an RR3 */
+	SCC_READ_REG(regs, SCC_CHANNEL_A, ZSRR_IPEND, rr3);
+
+	/*
+	 * Clear interrupt first to avoid a race condition.
+	 * If a new interrupt condition happens while we are
+	 * servicing this one, we will get another interrupt
+	 * shortly.  We can NOT just sit here in a loop, or
+	 * we will cause horrible latency for other devices
+	 * on this interrupt level (i.e. sun3x floppy disk).
+	 */
+
+	/* First look at channel A. */
+	if (rr3 & (ZSRR3_IP_A_RX | ZSRR3_IP_A_TX | ZSRR3_IP_A_STAT)) {
+		SCC_WRITE_REG(regs, SCC_CHANNEL_A, SCC_RR0, ZSWR0_CLR_INTR);
+		if (rr3 & ZSRR3_IP_A_RX)
+			scc_rxintr(sc, SCC_CHANNEL_A, regs, unit);
+		if (rr3 & ZSRR3_IP_A_STAT)
+			scc_stintr(sc, SCC_CHANNEL_A, regs, unit);
+		if (rr3 & ZSRR3_IP_A_TX)
+			scc_txintr(sc, SCC_CHANNEL_A, regs);
 	}
+
+	/* Now look at channel B. */
+	if (rr3 & (ZSRR3_IP_B_RX | ZSRR3_IP_B_TX | ZSRR3_IP_B_STAT)) {
+		SCC_WRITE_REG(regs, SCC_CHANNEL_B, SCC_RR0, ZSWR0_CLR_INTR);
+		if (rr3 & ZSRR3_IP_B_RX)
+			scc_rxintr(sc, SCC_CHANNEL_B, regs, unit);
+		if (rr3 & ZSRR3_IP_B_STAT)
+			scc_stintr(sc, SCC_CHANNEL_B, regs, unit);
+		if (rr3 & ZSRR3_IP_B_TX)
+			scc_txintr(sc, SCC_CHANNEL_B, regs);
+	}
+
+	return 1;
 }
 
 void