Troubleshooting DIMM Problems

C H A P T E R 2

This chapter describes how to detect and correct problems with the server’s Dual Inline Memory Modules (DIMMs). It includes the following sections:

DIMM Replacement Guidelines

How DIMM Errors Are Handled by the System

Isolating and Correcting DIMM ECC Errors

Note - Refer to the service manual or service label for the system that you are servicing for information on DIMM population rules.

DIMM Replacement Guidelines

Replace a DIMM when one of the following events takes place:

The DIMM fails memory testing under BIOS due to Uncorrectable Memory Errors (UCEs).

UCEs occur and investigation shows that the errors originated from memory.

More than 24 Correctable Errors (CEs) originate in 24 hours from a single DIMM and no other DIMM is showing further CEs.

Note - If more than one DIMM has experienced multiple CEs, other possible causes of CEs must be ruled out by a qualified Sun Support specialist before replacing any DIMMs.

Retain copies of the logs showing the memory errors to send to Sun for verification prior to calling Sun.

How DIMM Errors Are Handled by the System

This section describes the following topics:

Uncorrectable DIMM Errors

Correctable DIMM Errors

DIMM Fault LEDs

Uncorrectable DIMM Errors

For all operating systems, the behavior is the same for uncorrectable errors (UCEs):

1. When a UCE occurs, the memory controller causes an immediate reboot of the system.

2. During reboot, the BIOS checks the Machine Check registers and determines that the previous reboot was due to a UCE.

The uncorrectable ECC error is displayed in the service processor’s system event log (SEL) as shown here:

Memory | Uncorrectable ECC | Asserted | DIMM A0

Correctable DIMM Errors

If a DIMM has 24 or more correctable errors (CE)s in 24 hours, it is considered defective and should be replaced.

CEs will be captured in the SEL and light the fault LED after 24 single bit errors are detected in 24 hours. They are reported or handled in the supported operating systems as follows:

Windows server:

a. A Machine Check error-message bubble appears on the task bar.

b. Open the Event Viewer to view errors.

Access the Event Viewer through this menu path:

Start-->Administration Tools-->Event Viewer

c. View individual errors (by time) to see the details of the error.

Solaris:

Solaris FMA reports and sometimes retires memory with correctable Error Correction Code (ECC) errors. See your Solaris documentation for details.

To view ECC errors, use the following command:

fmdump -eV

DIMM Fault LEDs

When you press the Remind button on the motherboard (or memory tray for x4450), the LEDs next to the DIMMs flash to indicate that the system has detected 24 or more CEs in a 24-hour period on that DIMM.

DIMM fault LED is off: The DIMM is operating properly.

DIMM fault LED is flashing (amber): At least one of the DIMMs in this DIMM pair has reported 24 CEs within a 24-hour period or a UE (uncorrectable error).

See FIGURE 2-1 and FIGURE 2-2 for the locations of the Remind button and LEDs on the motherboard.

FIGURE 2-1 DIMMs and LEDs on Motherboard (X4150 and X4250)

Figure showing DIMMs and LEDS on the X4150 and X4250 motherboard.

FIGURE 2-2 .DIMMs and LEDs on Mezzanine (x4450)

Figure showing DIMMs and LEDS on the X4450 mezzanine.

Isolating and Correcting DIMM ECC Errors

If your log files report an Error Correction Code (ECC) error or a problem with a DIMM, complete the following steps until you can isolate the fault.

In this example, the log file reports an error with the DIMM in D0. The fault LED on DIMM D0 is on.

To isolate and correct DIMM ECC errors:

1. If you have not already done so, shut down your server to standby power mode and remove the cover.

2. Inspect the installed DIMMs to ensure that they comply with the DIMM population rules in your product service manual.

3. Press the Remind button and inspect the DIMM fault LEDs. See FIGURE 2-1 and FIGURE 2-2.

For CEs and UCEs, a flashing LED identifies the DIMM where the error is located.

4. Disconnect the AC power cords from the server.

Caution - Before handling components, attach an antistatic wrist strap to a chassis ground (any unpainted metal surface). The system’s printed circuit boards and hard disk drives contain components that are extremely sensitive to static electricity.

Note - To recover fault information, look in the SP SEL, as described in the Sun Integrated Lights Out Manager 2.0 User's Guide.

5. Remove the DIMMs from the DIMM slots.

Refer to your server’s service manual for details.

6. Visually inspect the DIMMs for physical damage, dust, or any other contamination on the connector or circuits.

7. Visually inspect the DIMM slot for physical damage. Look for cracked or broken plastic on the slot.

8. Dust off the DIMMs, clean the contacts, and install them.

Caution - Use only compressed air to dust DIMMs.

9. If there is no obvious damage, replace any failed DIMMs.

For UCEs, if the LEDs indicate a fault with the pair, replace both DIMMs. Ensure that they are inserted correctly with ejector latches secured.

10. Reconnect AC power cords to the server.

11. Power on the server and run the diagnostics test again.

12. Review the log file.

If the tests identify the same error, the problem is in the CPU, not the DIMMs.