Cisco Cisco UCS C22 M3 Rack Server White Paper

 

 

© 2015 Cisco and/or its affiliates. All rights reserved. This document is Cisco Public. 

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White Paper 

DIMMs:  Reasons to use only Cisco Qualified 
Memory on Cisco UCS Servers 

What You Will Learn 

This document explains why you should use memory that has been qualified to work 
with the Cisco Unified Computing System™ (Cisco UCS

®

) on Cisco UCS servers. 

Included are real-world images showing a Cisco UCS server damaged by using 
nonqualified memory.  

Cisco UCS servers use only dual in-line memory modules (DIMMs) that Cisco carefully selects, qualifies, and 

screens. Each DIMM must pass extensive hardware, software, and manufacturing tests to make sure it meets the 

highest standards and can perform reliably in Cisco UCS servers. Cisco UCS teams use only qualified DIMMs to 

optimize system design, firmware, and software development.  

Not all memory modules are created equal, and memory parts that have not been qualified by Cisco can result in 

issues and faults that can be difficult to trace to the DIMM itself. 

For each server CPU, Intel always tests and validates enterprise-class DIMMs from various DRAM vendors. Cisco 

f

urther carefully selects and qualifies DIMMs from Intel’s tested and certified DIMMs. DIMMs that do not meet 

Cisco standards may also fail to meet Intel’s DIMM certification criteria for its CPUs. In fact, DIMMs that Cisco does 

not qualify are often specifically rejected by Cisco vendors for one of many reasons and are sold to other suppliers 

on the gray market at a reduced price. 

Here are three reasons to use only qualified memory on Cisco UCS servers. 

1. Nonqualified memory can cause DIMM and server damage 

The industry has diverse requirements for memory, and what may seem to be an equivalent DIMM from one 
vendor may be vastly different from another vendor’s. Physical and electrical differences in DIMMs can result in 

immediate or eventual damage to the DIMM or server. In many cases, both the DIMM and the server are damaged 

when using memory that has not been qualified by Cisco. Please refer to the failure-analysis section of this 

document for real-life examples of this damage.  

Here are some differences between DIMMs that are qualified by Cisco and those that are not: 

● 

Vendors who sell qualified DIMMs build both DRAM and DIMM. This fact helps ensure that Cisco vendors 

use the best DRAM to build the modules and that they apply the strictest criteria for selecting, testing, and 

screening the highest-yield wafers and the DRAMs from these wafers for DIMM manufacturing. 

● 

DIMMs qualified by Cisco have 2D barcode that allows traceability all the way from the DRAM wafer to the 
customer’s system. This traceability is not possible with nonqualified DIMMs. 

● 

DIMMs qualified by Cisco meet all IPC rules for printed circuit assembly and inspection and are 

manufactured in a strict clean-room environment. Please refer to Figure 2 to see a nonqualified DIMM that 

was not manufactured in a clean room meeting these specifications.