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

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.