IBM System x3550 M4 Installation And Service Manual page 252

Figure 134. DVD drive cable latch
The following illustration shows cable routing for the DVD cable:
Attention: Follow the optical drive cable routing as the illustration shows.
Make sure that the cable is not pinched and does not cover any connectors or
obstruct any components on the system board.
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IBM System x3550 M4 Type 7914: Installation and Service Guide