Memory installation on Gen8 servers must follow a particular order:

HP ProLiant Gen8 model	Number of DIMM slots	Maximum Memory
DL380p Gen8	24	768GB
DL360p Gen8	24	768GB
BL460c Gen8	16	512GB
ML350p Gen8	24	768GB
SL230s Gen8	16	512GB
SL250s Gen8	16	512GB
SL270s Gen8	16	512GB

There are several advance features of DDR3 memory architecture when using HP ProLiant Gen8 servers with E5-2600 series processors:

• An increase to 4 memory channels per processor.
• A maximum memory speed of 1600 MT/s with the capability to support up to 1866 MT/s on future processor models.
• Support for HP SmartMemory with extended performance features over 3rd Party memory.
• Support for LRDIMM technology, which allows three quad-ranked DIMMs per channel.

DIMM Population Guidelines:

In the below picture you can see the memory configuration for 24-slot 2P ProLiant DL380p Gen8 Server. The white memory slots are used for each channel for each processor.

• When a single processor is installed in the system, install DIMMs in sequential alphabetical order – A, B, C, D and so on.

• When 2 processors are installed in the server, install DIMMs in sequential alphabetical order – P1-A, P2-A, P1-B, P2-B and so on.

• Within a given channel, user should populate DIMMs from the heaviest electrical load (dual-rank) to the lightest load (single-rank).

Please note when installing Quad Rank DIMMS in HP DL380p you must be installed them in the first socket of any memory channel in which they are populated. See the error message below.

238 – DIMM Configuration Error – Processor 1, Channel 2

Proliant Gen8 16 memory slot servers:
The picture below shows the memory slot configuration for 16 slot 2P ProLiant Gen8 servers.

Guidelines for DIMM types:

• You cannot mix Unbufferred non-ECC memory modules (UDIMMs), Registered ECC memory modules (RDIMMs), and Load Reduced Registered Ecc Modules (LRDIMMs).

• LRDIMMs are efficient for up to three DIMMs per channel.

• RDIMMs operates at 1.35 V or 1.5 V or can be used in any order, but the server will operate at the high voltage.

• Different speeds of DIMMs can be used in any order. The server will choose the lowest common speed.

Source: https://support.hpe.com/hpesc/public/docDisplay?docId=mmr_kc-0109346