diff -ruN linux-2.4.3/drivers/char/serial.c linux-2.4.3-patched/drivers/char/serial.c
--- linux-2.4.3/drivers/char/serial.c	Wed Mar  7 05:13:51 2001
+++ linux-2.4.3-patched/drivers/char/serial.c	Fri May 18 16:28:30 2001
@@ -1259,7 +1259,7 @@
 		serial_outp(info, UART_EFR, UART_EFR_ECB);
 		serial_outp(info, UART_IER, 0);
 		serial_outp(info, UART_LCR, 0);
-		serial_icr_write(info, UART_CSR, 0); /* Reset the UART */
+		/*		serial_icr_write(info, UART_CSR, 0); */ /* Reset the UART */
 		serial_outp(info, UART_LCR, 0xBF);
 		serial_outp(info, UART_EFR, UART_EFR_ECB);
 		serial_outp(info, UART_LCR, 0);
@@ -1364,9 +1364,12 @@
 	 */
 	serial_outp(info, UART_LCR, UART_LCR_WLEN8);	/* reset DLAB */
 
-	info->MCR = 0;
+	if (state->type == PORT_16C950)
+		info->MCR &= UART_MCR_PRESCALER;
+	else
+		info->MCR = 0;
 	if (info->tty->termios->c_cflag & CBAUD)
-		info->MCR = UART_MCR_DTR | UART_MCR_RTS;
+		info->MCR |= UART_MCR_DTR | UART_MCR_RTS;
 #ifdef CONFIG_SERIAL_MANY_PORTS
 	if (info->flags & ASYNC_FOURPORT) {
 		if (state->irq == 0)
@@ -2514,6 +2517,41 @@
 }
 #endif
 
+static int get_clock_prescaler(struct async_struct * info, unsigned char *value)
+{
+	unsigned char cpr;
+
+	if (!(serial_in(info, UART_MCR) & UART_MCR_PRESCALER))
+		cpr = 8;
+	else
+		cpr = serial_icr_read(info, UART_CPR);
+
+	if (copy_to_user(value,&cpr,sizeof(unsigned char)))
+		return -EFAULT;
+
+	return 0;
+}
+
+static int set_clock_prescaler(struct async_struct * info, unsigned char *value)
+{
+	unsigned char cpr;
+	
+	if (copy_from_user(&cpr,value,sizeof(unsigned char)))
+		return -EFAULT;
+
+	if (cpr < 8){
+		info->MCR &= ~UART_MCR_PRESCALER;
+	}
+	else{
+		info->MCR |= UART_MCR_PRESCALER;
+	}
+	
+	serial_out(info, UART_MCR, info->MCR);
+	serial_icr_write(info, UART_CPR, cpr);
+
+	return 0;
+}
+
 static int rs_ioctl(struct tty_struct *tty, struct file * file,
 		    unsigned int cmd, unsigned long arg)
 {
@@ -2668,6 +2706,14 @@
 			if (copy_to_user((void *)arg, &icount, sizeof(icount)))
 				return -EFAULT;
 			return 0;
+		case TIOCGSERCPR: /* Get serial clock prescaler */
+			if (info->state->type == PORT_16C950)
+				return get_clock_prescaler(info, (unsigned char *) arg);
+			return -ENXIO;
+		case TIOCSSERCPR: /* Set serial clock prescaler */
+			if (info->state->type == PORT_16C950)
+				return set_clock_prescaler(info, (unsigned char *) arg);
+			return -ENXIO;
 		case TIOCSERGWILD:
 		case TIOCSERSWILD:
 			/* "setserial -W" is called in Debian boot */
diff -ruN linux-2.4.3/include/asm-i386/ioctls.h linux-2.4.3-patched/include/asm-i386/ioctls.h
--- linux-2.4.3/include/asm-i386/ioctls.h	Fri Jul 24 20:10:16 1998
+++ linux-2.4.3-patched/include/asm-i386/ioctls.h	Thu May 17 16:34:08 2001
@@ -67,6 +67,8 @@
 #define TIOCGICOUNT	0x545D	/* read serial port inline interrupt counts */
 #define TIOCGHAYESESP   0x545E  /* Get Hayes ESP configuration */
 #define TIOCSHAYESESP   0x545F  /* Set Hayes ESP configuration */
+#define TIOCGSERCPR   0x5460  /* Get serial clock prescaler*/
+#define TIOCSSERCPR   0x5461  /* Set serial clock prescaler*/
 
 /* Used for packet mode */
 #define TIOCPKT_DATA		 0
diff -ruN linux-2.4.3/include/linux/serial_reg.h linux-2.4.3-patched/include/linux/serial_reg.h
--- linux-2.4.3/include/linux/serial_reg.h	Wed Mar  7 04:28:35 2001
+++ linux-2.4.3-patched/include/linux/serial_reg.h	Thu May 17 16:23:32 2001
@@ -121,6 +121,7 @@
 /*
  * These are the definitions for the Modem Control Register
  */
+#define UART_MCR_PRESCALER	0x80	/* Enable clock prescaler */
 #define UART_MCR_LOOP	0x10	/* Enable loopback test mode */
 #define UART_MCR_OUT2	0x08	/* Out2 complement */
 #define UART_MCR_OUT1	0x04	/* Out1 complement */