Lenovo ThinkCentre M90s Gen 2 Hardware Maintenance Manual page 45

e. External Cache
f. External Cache RAM
g. Hard disk drive
h. Diskette drive
3. Turn on the computer to retest the system.
4. Repeat steps 1 through 3 until you find the failing device or adapter.
If all devices and adapters have been removed, and the problem continues, replace the system board. See
Chapter 6 "Hardware removal and installation" on page 53.
.
Chapter 4 Service checkout and symptom-to-FRU index
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