Specifications
Part Number
M321RAGA0B20-CWK
Capacity
128 GB
Memory Type
DDR5 SDRAM, ECC Registered (RDIMM)
Speed
4800 MT/s (PC5-38400)
Rank & Organisation
4Rx4 (4 rank)
CAS Latency
CL40
Voltage
1.1 V
Pin Count
288-pin DIMM
Form Factor
RDIMM (registered, with on-module register and PLL)
ECC
Yes — sideband ECC
On-DIMM Power Management
PMIC (DDR5 standard)
Sub-channel Architecture
2 × 32-bit sub-channels per module
Target Platforms
Intel Xeon Scalable (4th/5th/6th gen) and AMD EPYC 9004/9005
Bandwidth per Module
38.4 GB/s peak
Overview
The Samsung M321RAGA0B20-CWK is a 128 GB 4-rank DDR5-4800 ECC registered DIMM. The M321R prefix identifies a DDR5 RDIMM, RAGA0B20 encodes the 128 GB 4Rx4 organisation and the -CWK suffix is the 4800 MT/s, CL40 speed and revision grade.
DDR5 moves the voltage regulator onto the module as a PMIC and splits the channel into two 32-bit sub-channels, which is why a single 128 GB RDIMM both raises capacity per slot and improves channel efficiency over DDR4 at the same frequency. Peak bandwidth per module is 38.4 GB/s.
Use 4-rank 128 GB modules when the platform's rank-per-channel budget allows it — they reach the highest capacity per DIMM slot, which matters on 2-socket servers with only 8 or 12 DIMM slots where the alternative is a much larger memory bill for 64 GB parts.
Key Benefits
128 GB per slot: maximum RDIMM density. DDR5-4800 ECC: 38.4 GB/s per module with sideband ECC. PMIC on-module: tighter voltage regulation at high rank counts.
Applications
In-memory databases and analytics, virtualization hosts, AI inference nodes holding model weights in RAM, HPC clusters, and large-scale VDI or cloud infrastructure.
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