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Green circuit board with black memory chips and gold contacts

A-Tech

A-Tech 16GB DDR4 2666 ECC RDIMM 2Rx8 for HP 835955-B21 server RAM

SKU CH-ZK5R-7SEYH

16GB DDR4 2666 ECC RDIMM server memory with registered 2Rx8 design for HP systems

  • Total capacity16 GB
  • Rated speedDDR4 2666 (PC4 21300)
  • ChipsetMajor Brand Chipset
  • CAS latencyCL19
  • Rated voltage1.2 V
  • Buffer typeRegistered
  • 16GB DDR4 2666 server memory expands capacity for heavier workloads
  • ECC RDIMM registered design detects and corrects data errors automatically
  • CL19 latency at 1.20V balances speed with standard DDR4 power draw
  • 2Rx8 dual-rank organisation increases memory density per DIMM slot
  • Tested compatible replacement for HP 835955-B21 and related part numbers

16GB DDR4 ECC RDIMM for HP servers

This 16GB DDR4 2666 ECC registered module replaces HP part numbers 835955-B21, 835955-B211, 835955-K21, 835955-S21, 838089-H21, 838089-K21, 840756-191, 840756-C91 and P18444-B21. It is built for server and workstation systems that require registered ECC memory. Buyers needing unbuffered UDIMM or non-ECC memory for desktop boards cannot use this module.

Sustained load behaviour with registered ECC

The registered design places a buffer on each command, adding one cycle of latency but reducing electrical load on the memory controller during continuous operation. ECC detects and corrects single-bit errors and detects multi-bit errors, protecting data integrity under heavy, long-running workloads. CL19 timing at 1.20V delivers stable throughput for virtualization, database and compute tasks that run for hours without reboot.

Installation notes and common issues

The 288-pin DIMM installs in standard DDR4 RDIMM slots; the registration notch position matches the HP-qualified pinout. Systems that require specific rank populations or maximum rank-per-channel limits may reject a 2Rx8 module if the platform firmware expects 1Rx4 or 1Rx8 configurations. Always verify the server memory population rules in the vendor documentation before installing.

How it compares

Measured against everything we stock in ECC Server RAM, at today’s prices. Recalculated every night.

Price $139.99
Cheaper than about 58% of the 6,523 comparable items (median $188.99).
Total capacity 16 GB
Lower than about 60% of the 6,064 comparable items (median 32 GB).
Price per GB $8.75 per GB
Pricier than about 62% of the 6,064 comparable items (median $7.25 per GB).

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Specifications

Product
Brand nameA-Tech
Total capacity16 GB
Performance
Rated speedDDR4 2666 (PC4 21300)
Processor
ChipsetMajor Brand Chipset
Memory
CAS latencyCL19
ECC supportYes
Buffer typeRegistered
Memory rank2Rx8
Power
Rated voltage1.2 V

Questions about this item

How much power does this 1.20 V DDR4 2666 registered module draw under continuous load?

It runs at the standard DDR4 voltage of 1.20 V. Actual power draw depends on the server platform and workload, so check your system documentation for detailed figures.

What must my server provide to use this 288-pin ECC RDIMM?

A DDR4 DIMM slot that supports registered ECC memory at 2666 MT/s, 1.2 V operation and 2Rx8 organisation.

Will this 2666 MHz CL19 module run reliably alongside slower DDR4 sticks already installed?

The module is rated for 2666 MHz CL19. When mixed with slower DDR4, the system typically clocks all modules to the lowest common speed and loosest timings.

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