There are no validated RDIMMs for the T140. It may be possible for the T140 to support RDIMMs, but we have not validated any at this time. Some of the processors supported on the T140 do not support buffered/registered memory. I suggest reviewing the specifications of the memory controller on the CPU, most Xeon CPUs support buffered memory.
You can find more detailed memory guidelines in the manual on the system support page.
Dell EMC, Enterprise Engineer
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