multi serial port communication

I am using Qnx4.25 on SCM 7026(a motherboard produced by shengbo in China). The motherboard can provide 6 serial port. Port 1,2 are original and the port 3-6 are extended port.

I have found the extended port(3-6) use the shared interrupt number 11
So I write the following sentenses to start the extended port in file–/etc/config/sysinit.1

/bin/Dev.ser -N/dev/ser3 D000,11 &
/bin/Dev.ser -N/dev/ser4 D008,11 &
/bin/Dev.ser -N/dev/ser5 D010,11 &
/bin/Dev.ser -N/dev/ser6 D018,11 &

but the system is crashed.

when I load one port, such as only one sentence
/bin/Dev.ser -N/dev/ser3 D000,11 &
the serial port 3 can work well.

who can tell me why? thanks…

Please do not cross-post,

What do you mean with “the system is crashed”?

What happens if you run after /bin/Dev.ser -N/dev/ser3 D000,11 (you said this works), the next one, for example: /bin/Dev.ser -N/dev/ser4 D008,11? (not from sysinit but from a shell to see the exit message)