Dell R640 Memory Incompatible Error (mixed Dimm)

Hello guys,

I need your advise why I received an error message on a Dell R640 with latest BIOS and iDRAC firmware.

We had originally 8 Samsung Dimms with Part number M393A8G40AB2 (64GB 2Rx4 PC4-3200AA) in the server.

We ordered new Dimm modules Dell certified from a reseller with the same part Number (Samsung M393A8G40AB2 - Dell par number SNPP2MYXC/64G), but somehow the server refuses to boot when mixing both new and original RAM modules.

Server boots fine with 2 or 4 or 8 new dimms. And boots fine with the old 2, 4 or 8 original dimms of course.

But when mixing original+ new dimms, it gives an error. Tried 8+8, 4+4, 2+2, nothing works.

Of course I followed the Dell memory population guide. Even with minimal boot (1 dimm per CPU) when mixing it does not boot.

Part numbers are the same except the last 5 characters (that seems the revision number, shoud not gives a difference?):

• original Dimms: M393A8G40AB2 – CWEC0 (64GB 2Rx4 PC4-3200AA - RA2 - 12 - MH1)

• new Dimms : M393A8G40AB2 - CWEBY (64GB 2Rx4 PC4-3200AA - RA2 - 12 - DC1)

Any ideas whats could cause the problem ? Any solutions you are thinking about?