Serial Port Too Slow...Why?

Serial Port Too Slow...Why?

Post by Brian Che » Tue, 03 Sep 1996 04:00:00



So I've been messing with PPP on my 28K modem for a few days.
Apparently I have a problem with the serial port.  Just using Kermit to
talk to the modem at any higher than 9600 baud (say to print out
settings "at&v") drops characters.  Dialing and connecting at higher
than 9600 baud causes characters to be dropped left and right.

Linux thinks (in autoconfig) that I have a 16550A.  Besides, I can use
my machine in Windows 95 to connect at 57.6 with no problems at all.  I
guess this is the mysterious part. Why can't my serial port handle any
better than that on Linux?  Why would the serial connection work fine in
Win95 and not in Linux?

Is there a problem with my serial I/O? I have on board serial support
that supposedly is compatible with the 16550.  Is there a way to
increase my buffer size so characters don't get dropped?  Is there some
gotcha with the serial I/O and Linux that I'm missing?  Is there a
better serial driver?  Sigh....


Oh, I'm using the 2.0.15 kernel and I have been using hardware flow
control on the modem.

 
 
 

Serial Port Too Slow...Why?

Post by Brian Che » Tue, 03 Sep 1996 04:00:00


So I've been messing with PPP on my 28K modem for a few days.
Apparently I have a problem with the serial port.  Just using Kermit to
talk to the modem at any higher than 9600 baud (say to print out
settings "at&v") drops characters.  Dialing and connecting at higher
than 9600 baud causes characters to be dropped left and right.

Linux thinks (in autoconfig) that I have a 16550A.  Besides, I can use
my machine in Windows 95 to connect at 57.6 with no problems at all.  I
guess this is the mysterious part. Why can't my serial port handle any
better than that on Linux?  Why would the serial connection work fine in
Win95 and not in Linux?

Is there a problem with my serial I/O? I have on board serial support
that supposedly is compatible with the 16550.  Is there a way to
increase my buffer size so characters don't get dropped?  Is there some
gotcha with the serial I/O and Linux that I'm missing?  Is there a
better serial driver?  Sigh....


Oh, I'm using the 2.0.15 kernel and I have been using hardware flow
control on the modem.

 
 
 

Serial Port Too Slow...Why?

Post by John Robinso » Thu, 05 Sep 1996 04:00:00


Quote:Brian Chen writes:
>I have been using hardware flow control on the modem.

                   ^^^^^^^^^^^^^^^^^^^^^
Is the cable made up right?

John.
--   _     _

| |_| / . \ ' \| ' \   5 Main Street, Auchencairn DG7 1QU, UK  +44 1556640 390
 \___/\___/_||_|_||_|  The company can't have this opinion even if it wants it
I'm goin' fishin'... Gonna bait me a line...                       --Chris Rea

 
 
 

Serial Port Too Slow...Why?

Post by Mike Campi » Fri, 06 Sep 1996 04:00:00


Have you cranked up the serial speed? Here's what I added to my rc.local:

            echo "Enabling RTS/CTS for modem."
            /bin/stty crtscts < /dev/cua1

            echo "Substitute 115kb when request 38.4kb."
            /bin/setserial /dev/cua1 spd_vhi

You might also want to set your asyncmap if you're running ppp. Check the
HOW-TO.

-Mike


>Brian Chen writes:
>>I have been using hardware flow control on the modem.
>                   ^^^^^^^^^^^^^^^^^^^^^
>Is the cable made up right?

>John.
>--   _     _

>| |_| / . \ ' \| ' \   5 Main Street, Auchencairn DG7 1QU, UK  +44 1556640 390
> \___/\___/_||_|_||_|  The company can't have this opinion even if it wants it
>I'm goin' fishin'... Gonna bait me a line...                       --Chris Rea

--
              __________________________
             /                          \
            /        Mike Campin         \

          /  http://www.ccsi.com/~campin/  \
         /__________________________________\

Life is much simplier if you don't know what is going on.

 
 
 

Serial Port Too Slow...Why?

Post by Mark Lo » Fri, 06 Sep 1996 04:00:00



>Is there a problem with my serial I/O? I have on board serial support
>that supposedly is compatible with the 16550.  Is there a way to
>increase my buffer size so characters don't get dropped?  Is there some
>gotcha with the serial I/O and Linux that I'm missing?  Is there a
>better serial driver?  Sigh....

Here are the universal solutions for serial port problems:

 1) Enable CTS/RTS ("hardware") handshaking in your modem.
 2) Enable CTS/RTS ("hardware") handshaking in your PC (default in Linux)
 3) If you use IDE hard disks, then upgrade to linux-2.0.17
    and then use "hdparm -u1" on your drives from /etc/rc.d/rc.local

--

For Linux IDE (big/many) help, see:  /usr/src/linux/Documentation/ide.txt
For latest Linux kernels: ftp.cs.helsinki.fi:/pub/Software/Linux/Kernel/v2.0/

 
 
 

1. Serial Port Too Slow...Why?

So I've been messing with PPP on my 28K modem for a few days.
Apparently I have a problem with the serial port.  Just using Kermit to
talk to the modem at any higher than 9600 baud (say to print out
settings "at&v") drops characters.  Dialing and connecting at higher
than 9600 baud causes characters to be dropped left and right.

Linux thinks (in autoconfig) that I have a 16550A.  Besides, I can use
my machine in Windows 95 to connect at 57.6 with no problems at all.  I
guess this is the mysterious part. Why can't my serial port handle any
better than that on Linux?  Why would the serial connection work fine in
Win95 and not in Linux?

Is there a problem with my serial I/O? I have on board serial support
that supposedly is compatible with the 16550.  Is there a way to
increase my buffer size so characters don't get dropped?  Is there some
gotcha with the serial I/O and Linux that I'm missing?  Is there a
better serial driver?  Sigh....


Oh, I'm using the 2.0.15 kernel and I have been using hardware flow
control on the modem.

2. Going mad with system()

3. serial port on v490 and Serial port on StorEdge 3510

4. a problem with fstat

5. Serial port to serial port copying software

6. setup Red Hat 5 and 3Com PCI (3c90x) ethernet

7. Send traffic from one serial port out to another serial port

8. Howto run linux on HP NetServer?

9. Serial port to serial port with null modem cable

10. Serial port - to - serial port networking

11. Serial port io too slow!

12. Serial Port Very Slow on Multia

13. linux serial port nullcabled to pc - slow start