Thanks for the help so far. Lots of people got the buffer flush issue figured out. Phil gets the prize for mentioning setvbuf. By changing printf from line buffering to no buffering all is well. Unfortunately no one had an answer to my more pressing problem of getting the serial port to initalize properly. The boot process doesn't appear to be using serial.conf yet it would also appear that setserial is not running in automatic mode and rewriting serial.conf either. I'd appreciate some pointers in how to follow the Slackware boot process to figure out who is setting things up improperly so I can fix them. Thanks again for all the help. -John >>> tclug-list-request at mn-linux.org 01/17/01 06:26PM >>> My serial port investigation continues. Here's the premise again... I've got an embedded system that dumps chars and strings to a serial port. I've attached a Slackware 7.1 Toshiba 430 CDT laptop to the other end of the serial cable. When the system streams a string of chars the linux box doesn't get anything but if I send individual chars they are received by the linux box. When I send 'setserial -ga /dev/ttyS0' it tells me my UART is a 16550A. If I change this to a 16550 everything works fine. I looked at /etc/serial.conf and it is defining the port as a 16450. Who's really controlling this and how do I get it set properly?