MPI run terminated on exception even with GDB

Hello,
I am trying hard to find a bug that causes ISA incompatibility across two different AMD opterons.

This is an MPI job and I issue the command on the frontend (named cluster) and the actual multithread job is running on a compute node (named compute-0-1). 


Problem is that, even if I run the MPI command under GDB, after the exception the process is terminated. So, I am not able to "disas" the program.

Please note that I compiled MPI and other applications with -g -Os (or -g -O2)

mahmood@cluster:tran-bt-o-40$ cat sc.sh
#!/bin/bash
ulimit -c unlimited
exec /share/apps/siesta/siesta-4.0/tpar/transiesta < trans-cc-bt-cc-163-20.fdf


mahmood@cluster:tran-bt-o-40$ cat hosts.txt
compute-0-1


mahmood@cluster:tran-bt-o-40$ gdb --args /share/apps/siesta/openmpi-2.0.0/bin/mpirun -hostfile hosts.txt -np 15 sc.sh
GNU gdb (GDB) Red Hat Enterprise Linux (7.2-90.el6)
...
Reading symbols from /share/apps/siesta/openmpi-2.0.0/bin/mpirun...done.
(gdb) run

...
--------------------------------------------------------------------------
mpirun noticed that process rank 0 with PID 11772 on node compute-0-1 exited on signal 4 (Illegal instruction).
--------------------------------------------------------------------------
[Thread 0x2aaaab5cf700 (LWP 25335) exited]
[Thread 0x2aaaab3ce700 (LWP 25333) exited]
[Thread 0x2aaaab1cd700 (LWP 25332) exited]
[Thread 0x2aaaaafcc700 (LWP 25330) exited]

Program exited with code 0204.
Missing separate debuginfos, use: debuginfo-install glibc-2.12-1.80.el6_3.6.x86_64 libibverbs-1.1.8-4.el6.x86_64 libnl-1.1-14.el6.x86_64 libudev-147-2.42.el6.x86_64
(gdb) disas
No frame selected.
(gdb)






If you have any idea about that, please let me know.



Regards,
Mahmood