Adding a lot of RAM to a Supermicro server

ytoledano · Jul 6, 2014

This is what I currently have:
Supermicro X9DR3-F
2x Intel Xeon 2690v2
128GB (8 x 16GB) 1866MHz DDR3 ECC Registered. Dual Rank. 1.5V

In the not too far future I want to upgrade to 256GB. I'm having a hard time understanding from the motherboard manual if it's OK to add 8 more 16GB dual rank sticks and what frequency the RAM will work at if I do.

This is the motherboard site:
http://www.supermicro.com/products/m...00/X9DR3-F.cfm

It's all pretty straight forward but the part that worries me is where it says "Populating RDIMM (ECC) Memory Modules" and there's a table underneath. In the table it says that only under certain conditions I will get 1866 mhz. I don't understand what's the difference between slot per channel and DIMM per channel. Also, I don't understand under which cell in the table each system falls in (the current and after the 128GB upgrade).

I appreciate any help!

Pinhedd · Jul 6, 2014

ytoledano :

Hi,

What the manual is telling you is that as you increase the number of ranks per channel (two ranks per DIMM in your case) it becomes increasingly harder to maintain signal integrity across the DRAM IO bus. Installing more than a certain number of ranks may result in certain data rates being unobtainable. DDR3-1866 may still be obtainable if you install more ranks, but Intel doesn't guarantee it and you may start seeing crashes.
The memory population in that chart is pulled from Intel's microprocessor specification. The number of slots per channel is the number of DIMM slots per channel that are present on the motherboard. The number of DIMMs is the number of slots per channel that are actually populated with memory modules. The top chart does not include entries for 3 DIMMs per channel because unregistered DIMMs are limited to two DIMMs per channel regardless of how many DIMM slots are present. The bottom chart for regisistered DIMMs includes entries for three DIMMs per channel.
Your motherboard has two sockets with four channels each and two slots per channel. Since you are using RDIMMs, this places your configuration on the left hand side of the lower chart. DDR3-1866 data rates are guaranteed only under single-DIMM configurations (single and dual rank only) as is seen under two slots per channel & 1 DIMM per channel.
If you wish to double your memory capacity by installing one additional DIMMs per channel (bringing the total to two) you will only be guaranteed DDR3-1600 data rates (2 slots per channel, 2 DIMMs per channel). You may still be able to obtain DDR3-1866 but it may not work.

Best of luck

ytoledano · Jul 6, 2014

Pinhedd :

ytoledano :

Hi,

What the manual is telling you is that as you increase the number of ranks per channel (two ranks per DIMM in your case) it becomes increasingly harder to maintain signal integrity across the DRAM IO bus. Installing more than a certain number of ranks may result in certain data rates being unobtainable. DDR3-1866 may still be obtainable if you install more ranks, but Intel doesn't guarantee it and you may start seeing crashes.
The memory population in that chart is pulled from Intel's microprocessor specification. The number of slots per channel is the number of DIMM slots per channel that are present on the motherboard. The number of DIMMs is the number of slots per channel that are actually populated with memory modules. The top chart does not include entries for 3 DIMMs per channel because unregistered DIMMs are limited to two DIMMs per channel regardless of how many DIMM slots are present. The bottom chart for regisistered DIMMs includes entries for three DIMMs per channel.
Your motherboard has two sockets with four channels each and two slots per channel. Since you are using RDIMMs, this places your configuration on the left hand side of the lower chart. DDR3-1866 data rates are guaranteed only under single-DIMM configurations (single and dual rank only) as is seen under two slots per channel & 1 DIMM per channel.
If you wish to double your memory capacity by installing one additional DIMMs per channel (bringing the total to two) you will only be guaranteed DDR3-1600 data rates (2 slots per channel, 2 DIMMs per channel). You may still be able to obtain DDR3-1866 but it may not work.

Best of luck

Thanks, that's very useful and makes sense.

1600 MHZ isn't too bad so upgrading is still an option. I'm also glad I didn't go with 32GB DIMMs, they would have been far more expensive and wouldn't have achieved 1866MHZ that I get today.

Pinhedd · Jul 6, 2014

ytoledano :

Pinhedd :

ytoledano :

Hi,

What the manual is telling you is that as you increase the number of ranks per channel (two ranks per DIMM in your case) it becomes increasingly harder to maintain signal integrity across the DRAM IO bus. Installing more than a certain number of ranks may result in certain data rates being unobtainable. DDR3-1866 may still be obtainable if you install more ranks, but Intel doesn't guarantee it and you may start seeing crashes.
The memory population in that chart is pulled from Intel's microprocessor specification. The number of slots per channel is the number of DIMM slots per channel that are present on the motherboard. The number of DIMMs is the number of slots per channel that are actually populated with memory modules. The top chart does not include entries for 3 DIMMs per channel because unregistered DIMMs are limited to two DIMMs per channel regardless of how many DIMM slots are present. The bottom chart for regisistered DIMMs includes entries for three DIMMs per channel.
Your motherboard has two sockets with four channels each and two slots per channel. Since you are using RDIMMs, this places your configuration on the left hand side of the lower chart. DDR3-1866 data rates are guaranteed only under single-DIMM configurations (single and dual rank only) as is seen under two slots per channel & 1 DIMM per channel.
If you wish to double your memory capacity by installing one additional DIMMs per channel (bringing the total to two) you will only be guaranteed DDR3-1600 data rates (2 slots per channel, 2 DIMMs per channel). You may still be able to obtain DDR3-1866 but it may not work.

Best of luck

Thanks, that's very useful and makes sense.

1600 MHZ isn't too bad so upgrading is still an option. I'm also glad I didn't go with 32GB DIMMs, they would have been far more expensive and wouldn't have achieved 1866MHZ that I get today.

You're most welcome.

Keep in mind that you have 8 fully independent memory channels. The increase in capacity from 128GiB to 256GiB would far outweigh the decrease in data rate from DDR3-1866 to DDR3-1600

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