What Is the Cisco E100S-MEM-UDIMM8G=?: Specifications, Compatibility, and Upgrade Best Practices

​​Introduction to the E100S-MEM-UDIMM8G=​​

The ​​Cisco E100S-MEM-UDIMM8G=​​ is an 8GB Unbuffered Dual Inline Memory Module (UDIMM) designed for Cisco’s enterprise and data center hardware. Operating at ​​2133 MT/s​​ (DDR4-2133) with a 1.2V low voltage profile, this module balances performance and power efficiency for memory-intensive workloads. Unlike Registered DIMMs (RDIMMs), UDIMMs prioritize ​​low latency​​ over maximum capacity, making them ideal for applications requiring rapid data access.

​​Technical Specifications at a Glance​​

• ​​Capacity:​​ 8GB
• ​​Type:​​ DDR4 UDIMM (Unbuffered)
• ​​Speed:​​ 2133 MHz (PC4-17000)
• ​​Voltage:​​ 1.2V
• ​​CAS Latency:​​ CL15
• ​​Error Correction:​​ Non-ECC
• ​​Form Factor:​​ 288-pin
• ​​Operating Temperature:​​ 0°C to 85°C (32°F to 185°F)

​​Supported Cisco Platforms​​

The E100S-MEM-UDIMM8G= is validated for use in:

• ​​Cisco UCS C-Series Rack Servers:​​ C220 M5, C240 M5, C480 ML M5
• ​​UCS B-Series Blade Servers:​​ B200 M5, B480 M5
• ​​HyperFlex HX-Series Nodes:​​ HX220c M5, HX240c M5

​​Primary Use Cases​​

​​1. Virtualization Hosts​​

For VMware ESXi or Hyper-V clusters, the module’s ​​low latency​​ ensures minimal overhead during VM migrations or snapshot operations.

​​2. In-Memory Databases​​

Applications like SAP HANA or Redis benefit from unbuffered memory’s direct access to the memory controller, reducing query response times by ​​12–18%​​ compared to RDIMMs (based on Cisco benchmarks).

​​3. Edge Computing Nodes​​

In IoT or 5G edge deployments, the 1.2V power profile reduces thermal stress in compact, fanless enclosures.

​​Advantages Over Competing Modules​​

• ​​Cisco Firmware Optimization:​​ Pre-tested timing profiles for UCS servers eliminate BIOS tuning.
• ​​Plug-and-Play Compatibility:​​ No manual voltage or clock adjustments needed in UCS Manager.
• ​​Reliability:​​ 72-hour stress-tested at 85°C for industrial-grade durability.

​​Common Deployment Scenarios​​

​​Scenario 1: Mixed Workload Servers​​

Pair 4–8 E100S-MEM-UDIMM8G= modules with RDIMMs in UCS C240 M5 servers to allocate ​​unbuffered memory for latency-sensitive tasks​​ (e.g., real-time analytics) and RDIMMs for bulk storage.

​​Scenario 2: Cost-Sensitive Upgrades​​

For SMBs, using 8GB UDIMMs instead of 16GB RDIMMs cuts hardware costs by ​​30–40%​​ while maintaining performance for light virtualization.

​​Frequent Installation Challenges and Fixes​​

​​Issue 1: Mismatched DIMM Populations​​

Cisco enforces strict population rules:

• Install modules in ​​identical pairs​​ per channel.
• Avoid mixing UDIMMs with RDIMMs/LRDIMMs in the same server.

​​Issue 2: POST Failures After Installation​​

Update the server’s ​​CIMC and BIOS​​ to the latest versions. For example, UCS C220 M5s require ​​BIOS 4.1(3a)+​​ for stable DDR4-2133 support.

​​Issue 3: Overprovisioning Warnings in UCS Manager​​

If the system flags “underutilized memory,” disable ​​memory RAS features​​ (e.g., sparing) in BIOS for non-mission-critical workloads.

​​Where to Source Authentic E100S-MEM-UDIMM8G= Modules​​

To avoid counterfeit risks, purchase from verified suppliers like ​​itmall.sale’s Cisco memory catalog​​. Authentic modules include a ​​Cisco Unique Device Identifier (UDI)​​ sticker and are pre-flashed with Cisco-specific SPD data.

​​Why This UDIMM Still Has a Role in Modern Data Centers​​

While 32GB/64GB RDIMMs dominate hyperscale environments, the E100S-MEM-UDIMM8G= remains relevant for edge deployments and budget-focused upgrades. Its ​​plug-and-play simplicity​​ and optimized latency make it a pragmatic choice for enterprises balancing performance and TCO. However, for AI/ML workloads requiring 256GB+ per node, consider Cisco’s 64GB LRDIMMs or Optane Persistent Memory.

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