840759-091 is the HPE assembly part number for 64GB (1x64GB) Quad Rank x4 DDR4-2666 CAS-19-19-19 Load Reduced Smart Memory Kit. This is the number you are most likely to find printed on the module label itself or returned by an HPE PartSurfer lookup. The module is a 288-pin DDR4 LRDIMM rated at 2666 MHz, PC4-21300, CL19 with 19-19-19 timings, running at 1.2 V. It is quad rank with x4 chip organization, an 8192 x 72 module configuration, and ECC data integrity checking. If the label on your DIMM reads 840759-091, the specifications on this page describe that module.
HPE Option Part #: 815101-B21
HPE Spare Part #: 850882-001
HPE Assembly Part #: 840759-091
PRODUCT SPECIFICATIONS FOR 840759-091:
- Type: DRAM
- Product Type: Memory module
- Form Factor: LRDIMM 288-pin
- Technology: DDR4 SDRAM
- Storage Capacity: 64 GB
- Registered or Buffered: Load-Reduced
- Data Integrity Check: ECC
- Module Configuration: 8192 x 72
- Chips Organization: X4
- Memory Speed: 2666 megahertz
- Memory Specification Compliance: PC4-21300
- Supply Voltage: 1.2 volt
- CAS Latency: CL19
- Latency Timings: 19-19-19
- RAM Features: Quad Rank
RESOURCES FOR 840759-091 (815101-B21)
Quickspecs for 815101-B21COMPATIBLE WITH:
PROLIANT BL SERIES
PROLIANT DL SERIES
PROLIANT ML SERIES
PROLIANT XL SERIES
** This list may not be complete. Contact us via Live Chat if you have any questions about compatibility.
FREQUENTLY ASKED QUESTIONS ABOUT 840759-091
What is the difference between 840759-091, 815101-B21 and 850882-001?
All three numbers identify the same physical 64GB DDR4-2666 LRDIMM. This page, 840759-091, is the assembly number, which is what typically appears on the module label and in PartSurfer output. 815101-B21 is the option number, used when the memory is ordered as a standalone kit. 850882-001 is the spare number, used for replacement parts. The DIMM is identical in every case; only the ordering context differs.
How do I confirm the module in my hand matches this page?
Check the label for 840759-091 and verify the printed specifications: 64 GB capacity, DDR4 SDRAM, PC4-21300 compliance, 2666 MHz, CL19, and 1.2 V operation. The module is a 288-pin LRDIMM, load-reduced rather than registered, quad rank with x4 chip organization and ECC. If those details line up, you are looking at the same part described here.
Which HPE servers accept this module?
This DIMM is supported in HPE Gen10 servers using 1st generation processors: BL460c Gen10, DL360 Gen10, DL380 Gen10, DL560 Gen10, DL580 Gen10, ML110 Gen10, ML350 Gen10, XL170r Gen10 and XL190r Gen10. Population rules for load-reduced memory vary by platform and processor count, so check the server QuickSpecs or memory population guide before installing.
Is this a registered DIMM or a load-reduced DIMM?
It is a load-reduced DIMM (LRDIMM). Load reduction buffers the data lines in addition to command and address, which is what allows a quad rank x4 module of this capacity to be used at DDR4-2666 speeds. Because of this, it cannot be mixed with registered DIMMs in the same server. The module includes ECC for data integrity checking.
What does the 8192 x 72 module configuration mean?
The 8192 x 72 figure describes the module's internal organization: 8192 megabits of depth by 72 bits of width. The 72-bit width is 64 bits of data plus 8 bits used for ECC, which is how the module supports error correction. Combined with the x4 chip organization and quad rank design, this yields the 64 GB total capacity listed for 840759-091.
HPE PARTSURFER INFO FOR 840759-091 (815101-B21)
| Spare PN | Description | |
|---|---|---|
 | 850882-001 | 64GB PC4-2666V-L, registered synchronous dynamic random access memory (SDRAM) 2Gx4, operated in a dual data rate (DDR4) mode, packaged in a dual in-line memory module (DIMM) organized as 8Gx72 |
Last Updated: 2026-09-26
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