Memory speed on a fully populated C460-M4: 1333 Mhz, 32 GB Dimm 2400 Mhz

[Walter Dey]

Customer has installed 96 dimm's in a C460-M4 (SAP Hana Node)

UCS-MR-1X322RU-G 32 GB DDR4-2133/2400 Mhz RDIMM/2R/x4/1.2v memory dimm's
However, even with all the tricks in the service profile, the operational speed of the memory is only 1333 Mhz.

According to the specification https://www.cisco.com/c/dam/en/us/products/collateral/servers-unified-computing/ucs-c-series-rack-servers/c460m4_specsheet.pdf

Table 10, the 32G RDIMM 2R with 3 DPC shows 1333 Mhz.

Can someone confirm, that this is max clock rate we can achieve with this configuration ?

[Paul Chapman]

Hi -

Based on the documentation and experience with other UCS servers, I agree with your assessment.  The system will detect the module capacity, rank (dual / quad), and quantity per channel and step the speed accordingly.

Based on the documentation, the only way to get higher memory speed (1600/1866) on this platform would be to change the quantity per channel, swap to quad-rank, or enable "lock-step"(lock-step is likely undesireable considering your question).

PSC

[Walter Dey]

Thanks Paul

Based on the documentation, the only way to get higher memory speed (1600/1866) on this platform would be to change the quantity per channel, swap to quad-rank, or enable "lock-step"(lock-step is likely undesireable considering your question).

- DPC cannot be changed, otherwise the total memory size is reduced

- lock-step: according to the documentation: https://www.cisco.com/c/en/us/td/docs/unified_computing/ucs/c/sw/gui/config/guide/1-4-1/b_Cisco_UCS_C-Series_GUI_Configuration_Guide_141/b_Cisco_UCS_C-Series_GUI_Configuration_Guide_141_appendix_010000.html

• Lockstep—If the DIMM pairs in the server have an identical type, size, and organization and are populated across the SMI channels, you can enable lockstep mode to minimize memory access latency and provide better performance. This option offers better system performance than Mirroring and better reliability than Maximum Performance but lower reliability than Mirroring and lower system performance than Maximum Performance.

-therefore the only solution would be swapping the memory Dimm's from dual to quad rank !