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Four green circuit boards with black memory chips and gold edge connectors

NEMIX RAM

NEMIX RAM 64GB (4x16GB) DDR4 2666 PC4-21300 CL19 ECC UDIMM memory upgrade for Synology RS3621xs+

SKU CH-7BSM-QP88M

64GB kit of four 16GB DDR4 2666 ECC UDIMM modules at CL19 for Synology RS3621xs+ NAS

  • Total capacity64 GB (4 × 16 GB)
  • Rated speedDDR4 2666 (PC4 21300)
  • ChipsetMajor OEM Samsung, Micron, Hynix
  • CAS latencyCL19
  • Buffer typeUnbuffered
  • Rated voltage1.2 V
  • ECC protection safeguards data integrity on Synology RS3621xs+
  • 64GB kit (4×16GB) expands NAS capacity for heavy workloads
  • DDR4 2666 CL19 matches system-rated speed and latency
  • 2V unbuffered UDIMM installs without extra cooling or voltage changes
  • Major-brand Samsung, Micron or Hynix chips ensure enterprise-grade reliability

Synology RS3621xs+ 64 GB DDR4 ECC kit

This 64 GB kit contains four 16 GB DDR4 2666 ECC UDIMM modules built for the Synology RS3621xs+ NAS. Each stick runs at 1.2 V with CL19 latency and uses a 2Rx8 organisation. The unbuffered design matches the system memory slots without requiring registered DIMMs.

Tool-free DIMM installation in minutes

Open the chassis, align the 288-pin modules with the slots and press until the latches click. No heat spreaders are fitted so clearance is minimal. The most common issue is mixing these ECC UDIMMs with non-ECC or registered memory, which prevents the NAS from posting.

Verify four free slots and ECC UDIMM support

Confirm the RS3621xs+ has four vacant DIMM sockets and that the firmware accepts 2Rx8 unbuffered ECC modules at 2666 MT/s. The platform must tolerate 1.2 V DDR4 without voltage offset. If the unit already contains different rank or voltage modules, replace the full set rather than mixing.

How it compares

Measured against everything we stock in Model-Specific Memory Upgrades, at today’s prices. Recalculated every night.

Price $496.99
Typical for this category: the median of 21,161 items is $397.99.
Total capacity 64 GB (4 × 16 GB)
Higher than about 60% of the 20,941 comparable items (median 32 GB).
Price per GB $7.77 per GB
Typical for this category: the median of 20,941 items is $8.19 per GB.

New to this? Buying memory and SSDs with crypto — what to check, what it costs to pay, and what is never asked for.

Specifications

Product
Brand nameNEMIX RAM
Product lineSynology Compatible Series NAS Memory
Model nameSynology DDR4 2666 MHz ECC Unbuffered UDIMM
Part numberME21300-628K4
Total capacity64 GB (4 × 16 GB)
Product type288-Pin DDR4 ECC UDIMM
Performance
Rated speedDDR4 2666 (PC4 21300)
Processor
ChipsetMajor OEM Samsung, Micron, Hynix
Memory
CAS latencyCL19
ECC supportYes
Buffer typeUnbuffered
Heat spreaderNo
Memory rank2Rx8
Power
Rated voltage1.2 V
Compatibility
Compatible systemsSynology
In the box
Included items64 GB (4 × 16 GB) DDR4 2666 MHz PC4-21300 2Rx8 1.2 V CL19 288-PIN ECC Unbuffered UDIMM KIT

Questions about this item

How can I confirm the 2666 MHz CL19 ECC UDIMM kit is running correctly after installing it in my Synology RS3621xs+?

Open DSM Control Panel, go to Info Center, and verify the system reports 64 GB total memory at 2666 MHz with ECC enabled.

What ships in the package and is anything else required for installation?

The box contains four 16 GB DDR4 2666 ECC UDIMM modules (part ME21300-628K4). No extra parts or tools are needed.

Which capacity version should I choose for the RS3621xs+ if I want the maximum supported memory?

This 64 GB kit (4 × 16 GB) fills all four DIMM slots and matches the RS3621xs+ maximum supported capacity.

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