When upgrading data center servers, reliability is the only metric that matters. The SK Hynix HMA81GR7CJR8N-XN is a staple in this environment.
As an 8GB DDR4-3200 RDIMM, this module is widely used in Dell PowerEdge, HPE ProLiant, and Lenovo ThinkSystem servers powered by Intel Xeon Scalable (Cascade Lake/Ice Lake) or AMD EPYC processors.
Built on the legendary Hynix C-Die (CJR), it offers a balance of speed and stability. This guide decodes the part number, breaks down the technical specs, and provides drop-in alternatives if you can't find stock.
Table of Contents
- 1. Decoding the Part Number
- 2. Technical Specifications Overview
- 3. The "CJR" Advantage
- 4. Equivalent Alternatives (Cross-Reference)
- 5. Conclusion
1. Decoding the Part Number
SK Hynix part numbers tell a detailed story. Here is the translation for HMA81GR7CJR8N-XN:
The Breakdown Matrix
| Segment | Code | Meaning |
|---|---|---|
| HMA | Module Type | SK Hynix DDR4 Module |
| 8 | Density | 8GB Capacity |
| 1G | Organization | 1Rx8 (Single Rank, x8 bit width) |
| R7 | Form Factor | RDIMM (Registered DIMM) |
| C | Die Gen | C-Die (3rd Generation 1x nm class) |
| J | Speed Base | High speed bin |
| R8 | Design | Reference Design Code |
| N | Temp | Commercial Temp (0°C to 85°C) |
| -XN | Speed Grade | 3200AA (3200 MT/s, CL=22) |
2. Technical Specifications Overview
This module is a Registered DIMM (RDIMM). It includes a Register Clock Driver (RCD) chip that buffers command and address signals, reducing the electrical load on the CPU's memory controller.
Specs at a Glance
- Capacity: 8GB
- Standard: DDR4-3200 (PC4-25600)
- Speed: 3200 MT/s
- CAS Latency: CL22 (22-22-22)
- Voltage: 1.2V
- Pin Count: 288-pin
- ECC: Yes (SECC)
- Rank: Single Rank (1R)
Why "1Rx8" Matters
1Rx8 means there is one group (rank) of memory chips on the module, and each chip has an 8-bit data width.
- Pros: Single Rank modules place the least load on the memory bus. You can typically populate 2 DIMMs per Channel (2DPC) without dropping memory speed (depending on the CPU architecture).
- Cons: Slightly lower interleaving performance compared to Dual Rank (2R) modules, but often cheaper.
3. The "CJR" Advantage
You might see "CJR" mentioned in enthusiast forums for overclocking, but in the server world, Hynix C-Die (CJR) is prized for Compatibility.
- Manufacturing Node: It is a mature 18nm (approx) process.
- Stability: It runs cooler than older A-die or M-die variants at 3200 MT/s.
- AMD Compatibility: CJR is famously friendly with AMD Ryzen/EPYC memory controllers, making this module an excellent choice for AMD EPYC 7002/7003 server deployments.
4. Equivalent Alternatives (Cross-Reference)
If the HMA81GR7CJR8N-XN is out of stock, you can safely mix or replace it with these electrically equivalent modules from other Tier-1 manufacturers. They share the same 1Rx8 3200AA spec.
Samsung Equivalent
- Part Number: M393A1K43DB2-CWE
- Specs: 8GB 1Rx8 PC4-3200AA-R
- Note: Samsung modules are the industry standard and are 100% compatible in mixed environments.
Micron Equivalent
- Part Number: MTA9ASF1G72PZ-3G2
- Specs: 8GB 1Rx8 PC4-3200AA-R
- Note: Micron is common in HPE and Dell OEM builds.
Procurement Tip: When mixing memory, ensure the Speed (3200), Rank (1R), and Width (x8) match. Do not mix RDIMMs (Registered) with LRDIMMs (Load Reduced) or UDIMMs (Unbuffered).
5. Conclusion
The SK Hynix HMA81GR7CJR8N-XN is a workhorse module for modern enterprise servers. Its Single Rank design allows for flexible population rules, and the CJR die ensures rock-solid stability. Whether you are expanding a cluster or replacing a failed stick, sticking to the 8GB 1Rx8 3200AA specification ensures seamless performance.
Sourcing Server Memory Need to upgrade your data center? Visit Aichiplink.com to search for HMA81GR7CJR8N-XN and compatible Samsung/Micron alternatives.
Written by Jack Elliott from AIChipLink.
AIChipLink, one of the fastest-growing global independent electronic components distributors in the world, offers millions of products from thousands of manufacturers, and many of our in-stock parts is available to ship same day.
We mainly source and distribute integrated circuit (IC) products of brands such as Broadcom, Microchip, Texas Instruments, Infineon, NXP, Analog Devices, Qualcomm, Intel, etc., which are widely used in communication & network, telecom, industrial control, new energy and automotive electronics.
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Frequently Asked Questions
What is HMA81GR7CJR8N-XN?
It is an 8GB DDR4-3200 1Rx8 RDIMM server memory module from SK Hynix with ECC support.
Is HMA81GR7CJR8N-XN compatible with desktop PCs?
No. This is a Registered ECC DIMM (RDIMM), which is not supported by most consumer desktop systems.
What does 1Rx8 mean?
1Rx8 indicates a single-rank module using x8 DRAM chips, offering good compatibility and lower memory bus load.
What speed does the “-XN” suffix indicate?
The -XN suffix denotes DDR4-3200 (PC4-25600) with JEDEC-standard CL22 timings.
Can this RDIMM be mixed with other brands?
Yes, as long as the modules match DDR4-3200, RDIMM, ECC, and 1Rx8 specifications (e.g., Samsung or Micron equivalents).
