After power on OSN 1500 alarm BUS_ERR was reported on the 5-CXL4. Host software is 188.8.131.52P01.
1) Checked host software version and board software version according to the matching table and everything was normal. Resetted the CXL boards. It didn't help.
2) The fourth parameter of the alarm is 0x02 which means - Type II BUS_ERR alarm, detected by active/standby cross-connect boards through the handshake.
First of all checked if the problem sticks to the slot or shift with the board when 4th and 5th boards are interchanged. After interchanging the CXL boards the alarm
was still in 5th slot. Then took another CXL board from spare parts and inserted it in 4th and then in 5th slot. In both cases alarm appeared in 5th slot. It means that
the problem is not in the board but in the slot.
3) Removed all boards from the subrack and checked the subrack inside. The pins on the 4th slot on the motherboard were bent. And there was no opportunity to
make them strait. The only solution is to change the subrack. See the pictures in the attached file.
1) Software version of CXL board mismatch.
2) Hardware problem with one of the CXL boards
3) Subrack and motherboard hardware problem.
If BUS_ERR alarm appears on the OSN equipment first check the software version with the matching table, then try to reset problem board, then change the problem
board with the one from spare parts and then finally change the subrack.