Thinkpad P71/Xeon (with ECC memory) - can I use two 32GB SODIMMS?

[wb0gaz_h]

Can I populate my P71 with two 32GB DDR4 ECC SODIMMS, one at the back of the machine and one under the keyboard (normally two devices would be in each area; I propose to use one double-capacity device in each area so that 64GB is available)?

Why?

My Thinkpad P71 is normally configured with four 16GB ECC DDR4-2400 SODIMMS. With that configuration, there are occasional crashes (Windows or Ubuntu Linux 18.04) and MEMTEST 10.4 reports a substantial number of recoverable (ECC) faults and occasional unrecoverable fault. Individually testing the modules (yielding 16GB, using MEMTEST 10.4) yielded a few recoverable faults but no unrecoverable faults. Testing them in pairs (either at back of machine or under keyboard, with the other location empty, for total of 32GB) yielded more recoverable faults and occasional unrecoverable fault. Contact cleaning was tried first to no avail (no improvement, no degradation.)

After further testing and experimentation, my current work-around is to populate only two of the SODIMMS (individually they test error free with MEMTEST 10.4), one in the area at the back of the laptop, one in the area under the keyboard. In this configuration there are no memory faults (per MEMTEST 10.4) and the machine runs normally, however, only 32GB memory is present.

Cause for failures when two modules occupy either or both of the socket locations is unknown. I speculate either capacitive loading or power problem, but those are only guesses based on symptoms.

I now ask if I can continue with the "one module per area" idea, but use a pair of 32GB ECC DDR4 SODIMMS, one in each area?

If this is viable solution, then I also ask about two parameters which may vary - 2400 MHz is the typical case for the 16 GB SODIMMS, however, 3200 MHz are now available. Is this OK? Cas Latency (CL) appears to be 17 for typical 16 GB ECC 2400 MHz SODIMM from major vendor, however, CL (where specified) appears to be 22 for 3200 MHz parts. Is this an issue?

Thank you for any advice,

Dave