DDR4 8GB, 16GB, 32GB Memory DIMM Issues With UEFI 2.10, IMM 1.95 Lenovo System x3850 X6 (6241), Lenovo System x3950 X6 (6241)

Resolving The Problem

Source

Symptom

When DDR4 8 GB (Option 46W0788), 16 GB (Option 46W0796), or 32 GB (Option 95Y4808) Registered DIMMs (RDIMMs) are installed in a system running Unified Extensible Firmware Interface (UEFI) version 2.10, Integrated Management Module II (IMM2) 1.95 with Memory Mode set to "Locked-step" (RAS mode), there is a high probability intermittent random training and memory test failures will occur during POST or run-time. As a result, DIMMs may be marked Disabled or Detected, unconfigured.

Memory errors may appear in one (1) of the following formats:

64 GB (Option 95Y4812) DDR4 LRDIMMs are not affected. These DIMMs require UEFI 2.10, IMM 1.95 as a minimal system firmware level.

Affected Configurations

The system may be any of the following IBM servers:

• Lenovo System x3850 X6, Type 6241, any model
• Lenovo System x3950 X6, Type 6241, any model

The system is configured with one or more of the following IBM Options:

• 16 GB TruDDR4 Memory (2Rx4, 1.2V) PC4-17000 CL 15 2133MHz LP RDIMM, Option 46W0796, any model
• 8 GB TruDDR4 Memory (1Rx4, 1.2V) PC4-17000 CL 15 2133MHz LP RDIMM, Option 46W0788, any model

This tip is not software specific.

The following system BIOS/uEFI level(s) are affected: UEFI version 2.10, Build ID A9E128p

The following system firmware level(s) are affected: IMMv2 version 1.95, Build ID TCoo12r

The system has the symptom described above.

Solution

This behavior will be addressed in a future UEFI firmware release.

The target date for this release is scheduled for First Quarter 2016.

The file is or will be available by selecting the appropriate Product Group, type of System, Product name, Product machine type, and Operating system on IBM Support's Fix Central web page, at the following URL:

     http://www.ibm.com/support/fixcentral/

Workaround

Multiple options:

If system is not running UEFI version. 2.10 (Build ID: A9E128p), IMM version. 1.95 (Build ID: TCoo12r):

   - Do not update to these versions if 8, 16 or 32 GB DDR4 RDIMMS are installed. (64 GB DDR4 LRDIMMs are not affected)

If system is already running UEFI 2.10, IMM 1.95 (or later):

1. When the affected DIMMs are installed (8, 16, 32 GB):
   - In the UEFI Setting menu, set Memory Mode: Independent mode.

Note: "Lock-step" is the default mode and may need to be changed to "Independent".

2. If users are unable/unwilling to change from "Lock-step" (RAS) mode:
   - Reduce memory speed to 1600 MHz in the UEFI setup menu.
   - If reducing memory speed is unacceptable, contact Support.

Additional Information

This issue is a result of low memory margins provided in the Memory Reference Code (MRC) only for 8 GB, 16 GB and 32 GB DDR4 RDIMMs.

Changing the memory mode provides improved margins as well as memory performance.

The Fix will contain the improved margins for all DDR4 RDIMMs.