[lug] 16550 Serial port buffering?

[Scott A. Herod]

Hello,

  We're having a hard time getting rapid response from a clock attached
to the 16550 serial port on my machine.  This is RH 7.1 with the
2.4.2 kernal.  We believe that we're seeing a big delay ( on the order
of 10 msecs ) between the time the clock sends a byte and the
time that select in a user-land process returns with that byte.

  A couple of questions:

  Is this an indication of context switching and if so is it possible
to speed it up?

  Is there a way to trigger another line on the serial port when the
read occurs so that I can watch a scope to verify that I am getting 
this delay?

  Any other thoughts would be greatly appreciated.

Thanks,

Scott