HPE P64984-B21 16GB PC5-51200 DDR5-6400MHz ECC CL52 1Rx8 1.1V Registered RDIMM Memory Module

P64984-B21 HPE 16GB PC5-51200 DDR5-6400MHz ECC CL52 1Rx8 1.1V Registered RDIMM Memory Module

The P64984-B21 HPE 16GB PC5-51200 DDR5-6400MHz ECC CL52 1Rx8 1.1V Registered RDIMM Memory Module represents a modern server-class memory solution engineered for latency-sensitive and reliability-critical environments. Designed to meet rising data throughput demands, this registered RDIMM (Registered Dual Inline Memory Module) leverages DDR5 technology to deliver higher bandwidth, improved power efficiency, and advanced error-correction capabilities. The module is specified as PC5-51200 (DDR5-6400), with ECC (Error-Correcting Code), CAS latency CL52, a 1Rx8 rank configuration, and a low operating voltage of 1.1V — making it a compelling choice for enterprise servers, virtualization hosts, cloud infrastructures, and high-performance computing nodes.

Key Technical Specifications and What They Mean

Memory Type and Speed

The P64984-B21 is a DDR5-6400 memory module, often listed as PC5-51200. DDR5 denotes the fifth generation of double data rate memory, providing significantly higher per-module bandwidth than DDR4. The numeric speed “6400MHz” (effective) indicates the peak data rate; when paired with modern server platforms, this speed reduces memory bottlenecks for data-intensive workloads.

Capacity and Module Density

At 16GB per DIMM, this module fits into a category ideal for capacity-optimized server builds that balance memory footprint and cost. 16GB modules are commonly mixed with higher density DIMMs in larger configurations, enabling flexible memory pool sizing across multi-socket systems.

ECC (Error-Correcting Code)

ECC capability is one of the defining features of server memory. The P64984-B21 features ECC, which detects and corrects single-bit memory errors automatically and flags multi-bit errors. ECC is essential for uptime and data integrity in mission-critical applications, such as databases, virtual machines, and in-memory analytics.

Registered (RDIMM) vs. Unbuffered (UDIMM)

This module is Registered (RDIMM), meaning it contains a register that buffers control signals between the memory controller and DRAM chips. RDIMMs improve electrical stability and support higher DIMM counts per channel—important for large-capacity server configurations. Registered modules trade a small latency overhead for greater scalability and reliability.

CAS Latency (CL52) and Rank (1Rx8)

CAS latency (CL52) measures the delay between a read command and data availability. While DDR5 increases raw bandwidth, absolute latency numbers change; CL52 is typical for high-frequency DDR5 modules and should be evaluated in the context of overall throughput and application sensitivity to latency. The 1Rx8 designation indicates a single-rank module with x8 DRAM chips, which impacts how the memory controller interleaves and accesses data; single-rank modules sometimes yield better compatibility and slightly different performance characteristics compared to dual- or quad-rank modules.

Voltage — 1.1V Efficiency

Operating at 1.1V, the P64984-B21 benefits from the power-efficiency improvements native to DDR5, enabling lower energy consumption per bit transferred. Reduced voltage helps in dense server environments where thermal load and power budgets are constrained.

Ideal Use Cases

Enterprise Virtualization

Virtualized environments (VMware, Hyper-V, KVM) benefit from fast, reliable memory because many VMs share the same physical resources. The P64984-B21 helps reduce memory contention and maintain consistent performance as VM density grows.

Database and In-Memory Applications

Databases such as PostgreSQL, MySQL, and in-memory stores like rely on predictable, high-throughput memory access. DDR5-6400 modules provide the bandwidth needed to support read/write-heavy operations and large working sets.

High-Performance Computing (HPC) and Scientific Workloads

HPC clusters and scientific simulations that process large datasets can leverage DDR5 memory bandwidth for improved compute-to-memory performance ratios, minimizing memory-related stalls.

Cloud and Web-Scale Infrastructure

Cloud providers and web-scale services require modular, scalable hardware. RDIMMs like the P64984-B21 help servers maintain signal integrity across high DIMM populations, improving service reliability.

Compatibility and System Integration

Ensuring system compatibility is critical. The P64984-B21 is optimized for HPE platforms and is commonly specified for HPE ProLiant servers and HPE-certified motherboards; however, compatibility depends on server BIOS versions, memory population rules, and memory speed negotiation between the DIMM and the system memory controller.

Latency vs Bandwidth Tradeoffs

DDR5’s higher frequencies come with adjusted CAS latency values (e.g., CL52). The net effect is usually improved overall throughput despite slightly larger CAS numbers. For most server workloads, increased bandwidth outweighs the small change in access latency.

BIOS/UEFI and Firmware Considerations

After installation, verify the server’s BIOS/UEFI and BMC firmware are up to date. Firmware updates often expand supported DIMM speeds and correct memory initialization quirks. Always follow vendor guidance for validated firmware before large-scale deployments.

Procurement, Part Numbers, and Lifecycle

The P64984-B21 part number is a vendor-specific SKU associated with HPE memory lines. When procuring, ensure you order exact SKUs or validated equivalents to meet warranty and support guarantees. Consider stocking spare modules for rapid hot-swap or field replacement where supported by the hardware.

Lifecycle and Future-Proofing

DDR5 adoption is ongoing; selecting DDR5-6400 RDIMMs positions systems for modern workloads while allowing future CPU/platform upgrades that take full advantage of higher memory bandwidth. When designing systems, consider balancing immediate capacity needs with upgradeability and slot availability.

Deployment Strategies to Maximize ROI

Consider phased upgrades that prioritize memory-bound nodes, run mixed-generation deployments where supported, and leverage memory balancing across clusters to extract maximum value from higher-bandwidth modules.

Comparisons: P64984-B21 vs Other Memory Types

Comparing this module to other options will help buyers choose the right balance of performance, capacity, and cost:

Vs. DDR4 RDIMM

DDR5 offers increased bandwidth and improved power efficiency. DDR4 modules (e.g., PC4 variants) may be cheaper, but they lack the higher throughput and some of the advanced on-die features of DDR5.

Vs. UDIMM (Unbuffered DIMM)

UDIMMs are common in desktops and some lower-end servers but do not scale as well in high-memory-count, multi-socket servers. RDIMMs are preferable in enterprise servers due to their buffering capabilities and support for larger memory populations.

Vs. LRDIMM (Load-Reduced DIMM)

LRDIMMs can often support even higher densities per module by reducing the electrical load on the memory bus, but they add complexity and cost. RDIMMs like the P64984-B21 typically strike a balance between performance, cost, and scalability for many enterprise environments.

Environmental and Power Considerations

Operating voltage of 1.1V contributes to lower power draw per DIMM versus higher-voltage generations. For dense deployments, these savings can be significant at scale. Evaluate thermal profiles and airflow in racks when populating multiple RDIMMs to maintain optimal operating temperatures.

Additional Resources and Further Reading

For technical teams requiring deeper validation, consult vendor technical whitepapers on DDR5 architecture, ECC behavior, and registered memory electrical design. Refer to HPE technical documentation for server-specific memory population rules, and consider vendor-provided memory qualification matrices during procurement planning.