IBM H Series Installation And Service Manual page 302

Attention: Use extreme care when lifting the I/O and system boards. Do not
allow them to bend at the connector.
13. Carefully slide the I/O and system boards toward the front of the system unit, tilt
the right side of the I/O and system boards upward and remove them.
14. Disconnect the system board from the I/O board.
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RS/6000 Enterprise Server Model H Series Installation and Service Guide