serial port "not found" on RHEL4 Dell 690s
 

I have four Dell 690s running RHEL4 (disks all cloned from 1 master, then made machine specific - names, ethernet ports, etc.) I have four copies of the same serial device (screen bezel with buttons), one plugged into each 690.

Only one 690 has a working serial port. The other three say that there is no such thing as /dev/ttyS0 when I try to initialize the port. (The same thing happens if I try to use ttyS1.)

All four 690s are running the same version of the BIOS, A04. I do an ls -las on /dev/ttyS*, and they all four show up as having /dev/ttyS0. The one 690 that works is using a reconditioned motherboard that we got as a replacement for the original which had a bad SAS disk controller.

What can I do or look at to try to fix this?

Thanks,

John