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Re: /dev/cua2 - modem problems! help!



On Wed, 26 Feb 1997, Jim Fetters wrote:

> problem: modem on /dev/cua2 is slow. when you type, it takes 5-7
> seconds to get an echo back from the AT commands on modem.
>
> symptoms: modem works fine when i boot into windows 95, also modem
> worked great under Slackware 2.0 (my previous install).
>
> dip doesn't work anymore, i can ATDT to my local internet provider,
> but it connects and there is a strange delay, and it only seems to
> want to return small chunks of words (12 chars or less), most of the
> data is missing. once again, everything works fine under win95, and
> when i had slackware up and running i never ever had a problem with
> the modem. (USR Sportster 28800)
>
> any advice?

1. use /dev/ttyS2 rather than /dev/cua2 - the cua devices are essentially
   obsolete.

   check to see that nothing else (getty, mgetty, etc) is trying to use
   the serial port on either the ttyS or cua device. the slowness may be
   being caused by some sort of locking/contention problem.

2. check that there's no IRQ or IO port conflict for the serial port.  
   try 'cat /proc/interrupts' and 'cat /proc/ioports'.  make sure they
   match a) your actual hardware (pull the machine apart if necessary)
   and b) your setserial commands in /etc/rc.boot/0setserial.

   if your sportster is an internal modem on ttyS2 (or dos "COM3:"), you
   will probably need to change it's IRQ so that it doesn't conflict
   with ttyS0 ("COM1:"). 

   IRQs can NOT be shared. 

   If possible, set it to an unused IRQ (5 or 7 work fine if you dont
   have a soundcard or other device using that IRQ...don't worry about
   the printer, linux uses polled IO for the printers by default rather
   than interrupt driven)

   If your internal modem doesn't allow you to change the IRQ, then try
   changing the IRQ on ttyS0 instead.

3. try using irqtune (in the hwtools package, i believe) to optimise the
   interrupt priorities for the serial ports.

4. make sure that the serial driver is either compiled into the kernel, or
   'serial' is listed in /etc/modules.  this will prevent kerneld from 
   unloading the serial module (and thus losing the setserial config)
   whenever the serial ports have been unused for a while.

craig


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