multi serial port communication

hi, 
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...

Qiang Li 			
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2009-02-13

Underwater Robot Research Center
ShenYang Insitute of Automation, Chinese Academy of Sciences
114# Nanta Street, ShenYang, P.R.China
Postcode:110016
Tel:86-024-23970211
EMail:liqiang@... ; liqiang_hn_cn@...