AC512779 Dell 256GB DDR5-4800MHz PC5-38400 8RX4 CL40 Ecc Registered Memory

Dell AC512779 256GB DDR5 Memory Kit

The Dell AC512779 represents a significant leap in server memory technology, providing exceptional density, performance, and reliability for modern data center and enterprise applications. This specific 256GB module is engineered to meet the rigorous demands of servers requiring high-capacity, fault-tolerant memory.

Core Product Specifications

Understanding the part number and its constituent specifications is crucial for proper system compatibility and procurement. The Dell part number AC512779 uniquely identifies this specific memory configuration within Dell's extensive inventory. The full product designation, Dell AC512779 256GB (1x256GB) DDR5-4800MT/s PC5-38400 8Rx4 CL40 1.10V ECC Registered 288-pin RDIMM, provides a complete technical breakdown of the module's capabilities. Each segment of this description conveys critical information about the memory's physical and electrical characteristics.

Detailed Memory Capacity

Memory capacity is a primary driver for server selection, directly impacting the number of virtual machines, database size, and application performance it can handle.

Unprecedented Single-Module Density: 256GB

This module offers a substantial 256-gigabyte (GB) capacity on a single Dual In-Line Memory Module (DIMM). This high density is achieved through advanced semiconductor manufacturing, utilizing high-density memory ICs (Integrated Circuits). A single server with multiple memory channels can achieve terabyte-scale total memory with fewer modules, which can be more power-efficient.

Kit Configuration: 1x256GB

The "1x256GB" notation specifies that this product is sold as a single, individual 256GB module. This allows for flexible server configuration and incremental memory upgrades. For optimal performance, servers are typically populated with identical modules across channels and, ideally, across all slots per processor, following the manufacturer's guidelines.

DDR5 Memory Technology

DDR5 SDRAM (Double Data Rate 5 Synchronous Dynamic Random-Access Memory) is the successor to DDR4, offering substantial improvements in speed, efficiency, and capacity.

Architectural Advancements Over DDR4

DDR5 introduces a revolutionary architecture compared to its predecessor. Key changes include the relocation of the Power Management IC (PMIC) from the motherboard to the DIMM itself, allowing for more granular and efficient power delivery. Furthermore, DDR5 modules feature a burst length of 16 (BL16) and two independent 40-bit sub-channels (32 data bits + 8 ECC bits each) per module, increasing efficiency and reducing latency in memory access patterns.

Benefits for Enterprise Workloads

The architectural shifts in DDR5 translate to tangible benefits for servers. The higher base data rates, improved channel efficiency, and greater bandwidth directly accelerate memory-intensive applications such as in-memory databases (e.g., SAP HANA), large-scale virtualization, high-performance computing (HPC), and data analytics platforms.

Performance Metrics

The performance profile of a memory module is defined by its data transfer rate, latency timings, and operating voltage.

Data Rate: 4800MT/s

The Dell AC512779 operates at a data rate of 4800 MegaTransfers per second (MT/s). A "transfer" is equivalent to two data operations per clock cycle (due to the "Double Data Rate" nature). This MT/s rating is the true measure of the module's data speed. A higher MT/s value indicates a faster data transfer capability, which reduces processing bottlenecks and improves overall system throughput.

PC5-38400 Module Classification

The designation PC5-38400 is the module's classification under JEDEC standards, derived from its peak bandwidth. To calculate this: (4800 MT/s * 8 bytes/transfer) = 38,400 MB/s (or approximately 38.4 GB/s) of peak theoretical bandwidth per module. The "PC5" prefix indicates a DDR5 module.

CAS Latency and Timings: CL40

The CL40 specification refers to the Column Address Strobe (CAS) Latency, which is the number of clock cycles between the memory controller requesting data and the first piece of data being available. A CAS Latency of 40 (at 4800MT/s) is a standard timing for high-density DDR5 RDIMMs. While this number is higher than typical DDR4 latencies, the significantly faster clock speed of DDR5 means the absolute time (in nanoseconds) is often comparable or better, resulting in robust performance for enterprise workloads that benefit more from bandwidth than ultra-low latency.

Operating Voltage: 1.10V

This DDR5 module operates at a nominal voltage of 1.10 volts. This represents a power efficiency improvement over DDR4, which typically operates at 1.2V. The lower voltage reduces the overall power consumption and heat generation of the server's memory subsystem, a critical factor in large-scale data center deployments where power.

Error Correction and Reliability Features

For mission-critical servers, data integrity is non-negotiable. The Dell AC512779 incorporates sophisticated error-checking and correcting technologies.

ECC: Error Correcting Code

The ECC (Error Correcting Code) feature is paramount for server stability. It enables the memory module to detect and correct single-bit memory errors automatically, without any operating system or application intervention. It can also detect, though not always correct, multi-bit errors. This proactive error handling prevents silent data corruption, system crashes, and application faults that can be caused by transient soft errors from background radiation or electrical noise.

Registered DIMMs (RDIMMs)

This module is a Registered DIMM (RDIMM). RDIMMs include a register (or buffer) on the module itself, placed between the memory controller and the DRAM chips. This register buffers the command and address signals, reducing the electrical load on the memory controller. This allows a server to support a greater number of memory modules and higher-capacity DIMMs per channel without signal degradation, which is essential for populating multi-socket servers with large amounts of memory. The trade-off is a slight increase in latency (typically one clock cycle) compared to Unbuffered DIMMs (UDIMMs), but this is a necessary and acceptable compromise for scalable server memory systems.

Physical and Electrical Interface

The physical design of the module ensures a secure and correct connection to the server motherboard.

288-Pin Edge Connector

The Dell AC512779 utilizes a 288-pin edge connector. This physical interface is specific to DDR5 technology and is not compatible with DDR4 (284-pin) or earlier generations. The pin count and keying notch position are designed to prevent accidental insertion into an incompatible memory slot.

Form Factor: RDIMM

The RDIMM form factor is the standard for enterprise servers. These modules are designed to be installed in server-grade memory slots, which often include robust locking levers to ensure a secure connection during shipping and operation, minimizing the risk of connection failures.

Rank and Organization: 8Rx4

The 8Rx4 designation is a critical but often overlooked specification. It describes the internal organization of the DRAM chips on the module.

Understanding "x4" Organization

The "x4" refers to the data width of the individual DRAM chips. In this case, each chip has a 4-bit wide data interface. To form a 72-bit wide RDIMM (64 data bits + 8 ECC bits), many such chips are used in parallel. This organization is common in high-density, high-reliability server memory.

Understanding "8R" or 8 Ranks

The "8R" indicates that the module is composed of 8 independent ranks. A rank is a set of DRAM chips that work together to cover the full data width of the memory bus. An 8-rank module is a very high-rank configuration, which is how the 256GB capacity is achieved. Server memory controllers have limitations on the number of ranks they can support per channel, so understanding the rank configuration is essential for compatibility when mixing and matching modules.

Compatibility and Intended Use Cases

This memory module is not a universal component; it is designed for specific Dell server platforms.

Designed for Dell PowerEdge and Other Enterprise Systems

The Dell AC512779 is engineered specifically for compatibility with select generations of Dell PowerEdge servers that support DDR5 memory and the 256GB RDIMM density. It is crucial to consult the official Dell documentation, such as the PowerEdge Technical Guide or the system's Owner's Manual, to verify compatibility with a specific server model (e.g., PowerEdge R760, R760xa, R660, etc.) and its configured processors.

Optimized Workloads

This high-density, high-bandwidth ECC memory is ideally suited for:

In-Memory Databases

Applications like SAP HANA, Oracle Database In-Memory, and other real-time analytics platforms that hold entire datasets in RAM for instantaneous query responses.

Server Virtualization and VDI

Consolidating a large number of virtual machines or hosting a vast Virtual Desktop Infrastructure (VDI) deployment requires massive amounts of reliable RAM to ensure smooth performance for all users and workloads.

High-Performance Computing (HPC) and AI/ML

Scientific simulations, financial modeling, and machine learning training tasks often process enormous datasets that must be held in memory, making high-capacity, high-bandwidth modules like the AC512779 essential.

Big Data Analytics

Platforms like Apache Spark that perform data processing in memory benefit tremendously from the large capacity and sustained bandwidth provided by these modules.