Hi Chris, this comes in a bit late, but hope it will be picked up. I know the details are a bit different, but this is the closest issue that I could find, so hope to pick up the thread here.
I have a R810, that started out at Bios 1.2.0. It contained 16 x 16GB RAM (SNPMGY5TC/16G) which booted fine. The system has 4 x E7450 CPUs installed. The memory is/was installed in the white tab slots, x1 - x2 - x3 - x4. The other slots were populated by plastic blanks to keep proper airflow..
When upgrading this system to the latest available Bios, 2.9.0, the system showed a brief Dell logo, before stopping on a "System Halted" message.
I tried replacing the memory with 16 x 8GB RAM, and the system booted again (with suboptimal RAM config warning, but functioning fine).
Troubleshooting further, I found the 2.1.0 Bios to be the one to break compatibility with the 16GB RAM sticks. In the release notes, that Bios does indicate a significant amount of microcode updates.
When looking into the SNPMGY5TC/16G RAM stick details, they mention the need for an E7 CPU to run. I believe the E7450 should be compatible (as it did indeed work on older Bios), but I have also recently upgraded to 4 x E7 4870 CPUs, repeated the troubleshooting steps above, but with same results.
So, to summarize:
SNPMGY5TC/16G should be compatible with R810 (4 x E7 4870 CPU), is positioned in white tab memory (x1 - x4) slots according to the config in owner manual:
Total mem: 256
DIMM size: 16
Number of DIMMs: 16
The system does show VGA screen, but goes directly to "System Halted" message.
A direct replacement back to 8GB sticks (1:1, same slots) brings the system back to life. The 16GB sticks worked fine in pre-2.1.0 Bios (with any CPU). Memory tests running on Bios 1.2.0 indicate no error on 16GB sticks. I have tested the sticks with 8 installed at a time (instead of 16), and then replacing them with the other 8. Both give same "System Halt" result.
It seems clear that the problem lies in compatibility after the microcode in Bios 2.1.0 and later.
Do you have any more information you could provide on this? Any suggested further tests I could do?
With my R910, I had to populate a minimum of TWO DIMMs per memory cartridge/riser. So the minimum number of DIMMs needed to get the thing to boot was:
2 DIMMs in every other cartridge (empty cartridges are more or less ignored), which means 2 DIMMs per CPU. The R910 has 4 CPUs, so I had to populate every other cartridge (each CPU gets 2 cartridges) with 2 DIMMs for a total of 8 DIMMs. The pair of DIMMs should go on the top two slots (Slots 1 and 2) of each populated cartridge.
I think you may need to populate DIMMs two at a time. So for example, you may get the error message if you have 3 DIMMs in each cartridge. I would start with the "minimum" (2 DIMMs per cartridge or 0 DIMMs, at least 2 DIMMs per CPU) and ensure it boots with that.
What's more, it looks like the two DIMMs you populate each riser with must be the same. I was unable to POST with every other riser populated with an 8GB and a 16GB DIMM in Slots 1 and 2. If this is correct, then you will need a minimum of 8 of the same exact DIMM (maybe capacity just needs to be the same but I suspect it's more than that) for an R910 with 4 CPUs to even boot.