for new users with memory issues !!!
The the 2 year 11 month old XPS 8910 Service Manual I downloaded is wrong TWICE
1. slots for memory pairs
just put ram in 2 white slots or 2 black slots pairs
2. memory matrix
just add memory in pairs for dual channel 4 / 8 / 16 / 32 up to 64gb total
There are a lot of errors in addition to those you mentioned:
1. The Note above the Memory configuration matrix is incorrect. It should read "... slots DIMM1 and DIMM2 ..."
2. The headings in the matrix are incorrect. DIMM2 should be DIMM3 and DIMM3 should be DIMM2.
3. Not all available configurations are listed in the matrix. A single 8GB or 16GB memory module (single channel mode) will work, also two 16GB memory modules for a total of 32GB will work.
4. Some of these errors are in the service manuals for the XPS 8920 and XPS 8930.