Thanks for the pointers Daniel, I installed all the ram sticks and got it to boot with 192GB installed, but still need to have an 8Gb in A1/B1 so I am not able to run matched pairs in each slot for optimal configuration.

I see that the iDRAC is running firmware 2.61.60 (build 8) with settings version 1.65.65.04, which I believe is current?

The memory mode only seemed to have the one option, optimzer, so that is selected.

I will run windows memory diagnostics tonight, but not sure that will explain why I cannot run 16Gb in A1-4 and 8Gb in A5-8.

What would be the maximum time the "configuring memory..." might need and still be expected to complete successfully? It seems as if it takes more than 20 secs, then it never completes?

Hello

I'm not seeing any obvious issues, based on the information provided. M393B2G70BH0-CK0 is a supported module on the R720XD. The memory population of 16GB in 1-4 and 8GB in 5-8 is supported. The configuration you are using for testing of a single 16GB module in slot 1 on both lanes should work.

I would check the memory mode to make sure it is set to optimizer. If you haven't been disconnecting power when swapping memory around then start doing that, aside from safety it will drain flea power. Make sure the iDRAC/LCC is at the most current revision. If there is a hardware profiling issue with the new memory then a FW update may resolve. Also, check the current setting of Collect System Inventory on Reboot.

http://www.dell.com/poweredgemanuals/

http://www.dell.com/idracmanuals/

Thanks

I am still struggling with this. Although it booted all the way to Windows one time with 192GB installed, the next time it seemed to hang on the Configuring Memory again and so I went back to the original 8x8GB configuration and all was well. 

Now when I try to introduce the 16GB sticks in pairs, it takes around 20 seconds to get to Configuring Memory...Done, then IDRAC...Done, then it goes straight back to Configuring Memory... and never seems to complete. I typically leave it an hour there before giving up in disgust. 

Should I leave it longer, and if so, how much longer?

Is there any one configuration of the 8GB and 16GB sticks that is likely to be more successful, or they should all be bootable, even if not optimal for speed, etc?

I have it running, with 192 Gb installed, but it HAS to have 8 Gb sticks in A1/B1, then I have 16Gb in A/B 2,3,4, back to 8 Gb for A5/B5, 16Gb in A6/B6, and 8Gb in A/B 7&8.

Any ideas what impact on performance from this configuration? All are running at 1600 MHz, but am I losing anything else here?

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@John2019 wrote:

I have it running, with 192 Gb installed, but it HAS to have 8 Gb sticks in A1/B1, then I have 16Gb in A/B 2,3,4, back to 8 Gb for A5/B5, 16Gb in A6/B6, and 8Gb in A/B 7&8.

Any ideas what impact on performance from this configuration? All are running at 1600 MHz, but am I losing anything else here?

 

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That type of configuration would normally be blocked, but the R720XD has the "flexible memory" feature. Flexible memory allows non-optimal configurations that we do not support. Anything allowed by the memory controller should function. If you mix different size memory within a memory grouping(1,2,3,4) the memory will operate in single channel mode. This will limit data transfer to the speed of a single module. Normally, it will spread the data across the channels like a RAID 0. In single channel mode it will operate like concatenation, fill up the first module then the second and so on. It may not be exactly like concatenation, but that should give you an idea of the performance impact.

Thanks