Hello The reason it is not optimal is because you are mixing DIMMs within a bank. The system supports tri-channel memory. It does this by spreading a bank of memory across 3 channels. Here are how the banks are set up: DIMM 0 - 1,2,3DIMM 1 - 4 For an optimal configuration the DIMMs in slots 1,2,3 shoud be identical. In older systems that do not support flexible memory configuration the DIMMs in slots 2,3 would be disabled. Since this system supports flexible memory configurations it will allow the DIMMs to stay, but gives the non-optimal error. If you mix memory in this system you can only have 1 unlike DIMM installed for an optimal configuration. The optimal configuration that uses the maximum memory for the DIMMs you have available would be: 8GB - 1,24GB - 4 The best non-optimal configuration would be: 8GB - 1,24GB - 3,4 That configuration will still give you errors, but is better than the current configuration.   This doesn't mean that you have to have identical DIMM modules in the channels. It means that the channels must be populated the same. Here is an example: DIMM 0 = slots 1,2,3DIMM 1 = slots 4,5,6 Chanel 0 = 1,4Channel 1 = 2,5Channel 2 = 3,6 You can have DIMMs of different rank, speed, and capacity mixed across the channels, but you cannot have different configurations. For instance, in this configuration if you populated slots 1,2 with DIMMs then the only valid configuration for DIMM 1 would be populating a single DIMM in slot 4(If the system did not require DIMMs to be installed in pairs) or 2 DIMMs in slots 4,5. You could not populate a DIMM in slot 6 since the first slot(3) in the channel(2) is not populated. The channel population rule basically means that you cannot populate the second slot in a channel if the first slot is not populated. In your system slot 1 and 4 are in channel 0. All other channels only have a single slot assigned to each memory controller. As long as you have a DIMM in slot 1 you can populate slot 4. Memory population rules can be very confusing. If you have any more questions let me know. Thanks
Hello Everyone, Let me start off by stating our current memory configuration (Dell PowerEdge T410): We only have one processor installed, so we have 4 DIMM slots to use A1-A4. Only 3 are currently installed as: A3: 4GB 2Rx8 1333 A2: 4GB 2Rx8 1333 A1: 4GB 2Rx8 1333 A4: blank as it currently stands, our server (running sbs2011) is extremely slow, and we have traced this to RAM usage. That being said, I went to Dell's online store and purchased 2 8GB 4Rx8 1066 RAM sticks to use in the server. I figured I would take one 4 GB module out, so I would then have 24GB total (2 4GB + 2 8GB).   Reading the the hardware manual, i see that mixing 2rx8 and 4rx8 is supported as long as the 4rx8 is in the white slot (first slot of the channel). I also see that mixing capacities of ram is supported as long as each channel has an identical configuration. I assumed this meant as long as each channel had the same capacity. So I was thinking 8GB in each channel: A3: 8GB (channel 2) A2: 8GB (channel 1) A1: 4GB (channel 0) A4: 4GB (channel 0)  I placed the DIMMS in this configuration thinking I was all set until I booted the server, and I get a DIMM mismatch error and the BIOS says unsupported memory configuration. However, the server boots into windows and it says 24 GB and acts normally. What am I missing? Should I be concerned? How can i fix this?  Any input would be greatly appreciated. Thanks so much!
PowerEdge T410 Memory Configuration