Dell PowerEdge R330 Owner's Manual page 56

Figure 18. Inside the system—with four 3.5-inch cabled hard drives
1. hard drive (4)
3. power supply unit (2)
5. memory module socket (4)
7. system board
9. intrusion switch
11. control panel assembly
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2. power interposer board
4. expansion card riser
6. processor
8. cooling fan (4)
10. optional optical drive or 1.8-inch solid state drives
(optional)