726718-B21 HPE 8GB DDR4-2133 Single Rank x4 Memory Kit

726718-B21 is a registered DDR4 kit holding one 8GB single-rank x4 DIMM, rated DDR4-2133 at CAS-15-15-15 and 1.20V. In PartSurfer the option maps to spare 774170-001, an 8GB 2133MHz PC4-2133P-R single-rank x4 RDIMM, and that spare is flagged as used in more than 200 HP products, which says how widely this one DIMM type was fitted across Gen9 builds.

The x4 in the name is the part people trip over. HPE also sold 8GB modules built as x8 devices, and the two are not interchangeable by label. For example, one 8GB PC4-2133P-R spare in PartSurfer's BL460c Gen9 list is dual-rank x8, a different organisation from this one. Rank and device width determine how a DIMM counts against the per-channel limits in HPE's configurator, so match 1Rx4 to 1Rx4 when extending an existing bank.

HPE's DDR4 Smart Memory QuickSpecs revision history records this SKU as added to the Models section in June 2018, so it is part of the maintained Gen9 range. As with every registered DDR4 kit it cannot share a server with load-reduced DIMMs, and DDR3 modules will not fit the DDR4 sockets.

For other sizes at the same speed look at 726717-B21 (4GB) and 726719-B21 (16GB). If the host is a BL460c Gen9 running 2400 MT/s memory, the 8GB option listed there is 805347-B21. Server-side parts are in the HPE and other server parts hub.