EDIT: here are some updates after opening the keyboard and accessing the primary memory modules:
- Update 1: the laptop had a 32GB SODIMM in DIMM_A. I installed another 32GB SODIMM into the other primary slot - DIMM_C. The laptop then booted just fine (as expected) with total of 96GB.
- Update 2: I then relocated the other SODIMM from DIMM_B to DIMM_D, and the laptop still boots fine with 96GB seen.
I just acquired a used Dell Precision 7760 laptop from eBay. It's working fine, so I thought I would upgrade RAM. The laptop came with a SODIMM module installed in "slot 3" (as per CPU-Z) which I don't know whether that's DIMM_A or DIMM_C, but it's definitely one of the 2 primary module slots under the keyboard. I have not gotten to opening up the keyboard to access the primary module area, so I thought I'd put an extra 32GB matching SODIMM in DIMM_D (which is on the much more conveniently accessible bottom section of the laptop). The laptop did not boot, with 2 amber lights and then some white lights (sorry, forgot to count precisely). I then switched the new SODIMM into DIMM_B on the bottom side, and the laptop boots and I see 64GB installed. BIOS did report only 1 memory channel active so my guess is that the primary slot corresponding to DIMM_D is not populated, which may hopefully explain the non-boot situation.
I have studied the service manual as well as the spec / setup PDFs, but am unable to get clarity on 2 things, so would love if anyone can help with these questions:
1. How do the DIMM_[A/B/C/D] slots correspond to "Slot 1/2/3/4" in CPU-Z?
EDIT: DIMM_A is "slot 3" in CPU-Z per my later updates
2. More importantly, is it a known requirement that both the primary modules should be populated first before their corresponding secondary module slots are filled?
EDIT: empirically, this does seem to be proven that you need a SODIMM in the primary slot corresponding to the secondary slot you are trying to fill, else the laptop does not boot.
Thanks in advance!
