XPS 8930, DIMM slots

Why don't you just put them where they are supposed to be?

Since it is working I would leave it as it is. First, the Note on page 76 of the Service Manual is wrong. If you look at the System Component Diagram on page 18 you will see that DIMM 1 has a white memory securing clip and DIMM 3 has a black memory securing clip. Memory should be added in pairs with similar colored securing clips. So the Note should say DIMM 1 and DIMM 2. Table 2 is also wrong. The columns should be headed DIMM3 and DIMM2 should be swapped. If you follow the Note it will probably work but instead of your 16 GB memory operating is dual channel mode it will operate in single channel mode just like when you have the single 8 GB memory module.

It seems the right place is where they are now because they are working. The OP did not say but CPU-Z should be reporting Dual under Channel # on the Memory tab. If you know the right locations for the memory module then tell us because the Service Manual is wrong. The errors in the Service Manual was reported here months ago and the similar errors appear in the service manuals for the XPS 8910 and XPS 8920.

So why not put them in the right place to remove all doubt?

When looking at the XPS 8930 Service Manual motherboard layout,

Page 18 states the DIMM configuration as =
27 White DIMM 2
26 Black DIMM 4
25 White DIMM 1
24 Black DIMM 3
(CPU)

We can debate the numbering, I think it should have been =
27 White DIMM 3
26 Black DIMM 4
25 White DIMM 1
24 Black DIMM 2
(CPU)


But based on those published numbers, a 16GB (2x8GB) configuration should be installed like this =
(CPU) Black DIMM 3    White DIMM 1    Black DIMM 4    White DIMM 2
                                     8GB                                               8GB

The OP wrote, "The BIOS then booted properly on to WIndows 10.  I did a Windows 10 memory check tool and found no errors.  I then ran CPU-Z and confirmed that DIMM 2 and DIMM 4 had 8GB each of DDR4 SDRAM for a total of 16GB." Perhaps you have a different definition of working correctly.

Chris, I think page 18 in the Service Manual is correct because the DIMM slots are labeled XMM3, XMM1, XMM4, and XMM2 on the motherboard; I believe this because that is the way it is in the XPS 8910.and I don't think it has changed.

My version is what the OP wrote. You question the OP's results ("But working correctly?") and I pointed out what the OP wrote. No adverse effects now, not sure about the future or how to test for that in the present.

I am not debating that a white+black configuration works to show 16GB in BIOS and Windows. I am just stating that the service manual does specify for two memory stick configurations, white should go with white and black with black. Which is why I just omit all numbering and write to colors instead =

8GB = (CPU) Black empty, White 4GB, Black empty, White 4GB
16GB = (CPU) Black 4GB, White 4GB, Black 4GB, White 4GB
16GB = (CPU) Black empty, White 8GB, Black empty, White 8GB
24GB = (CPU) Black 4GB, White 8GB, Black 4GB, White 8GB
32GB = (CPU) Black 8GB, White 8GB, Black 8GB, White 8GB
64GB = (CPU) Black 16GB, White 16GB, Black 16GB, White 16GB
* 48GB = (CPU) Black 8GB, White 16GB, Black 8GB, White 16GB

* Not validated by Dell but works.

Chris, I agree with you that it is simpler to ignore the numbering and go with pairing based upon the color of the memory securing tabs when installing memory in pairs although Dell does sell configurations with a single memory module as in this case where the OP originally had 8 GB with a single memory module.

I didn't see where they said they ran CPU-Z, also I see no place to cancel a post.

CPU-Z was mentioned in the first post of this thread. I don't know about cancelling a post, but your can edit it.