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lsdejones
1 Copper

Dell R610 "Unsupported memory configuration" bios message

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Hey,

I have a Dell R610 that I just put more ram into and I get the message on boot "Unsupported memory configuration".

On reboot it says "F1 to continue or F2 for setup", if I press F1 the server boots up fine, all the memory shows up, and everything works great.

I have also run the Dell hardware memory test and it came back with no faults so the memory is good too.

So, it seems the server is fine with the new memory, and all the memory checks out as good, but the bios message concerns me ... can anyone enlighten me to what it means and how to resolve it?

Note: if it helps this is the original slot configuration if you were to look down at the server from the front:

[2G][empty] [2G][empty] [2G][empty]    [CPU]    [CPU]    [empty][2G] [empty][2G] [empty][2G]

Now its like this:

[2G][2G] [2G][2G] [8G][empty]    [CPU]    [CPU]    [empty][8G] [2G][2G] [2G][2G]

Thanks,

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theflash1932
6 Indium

Re: Dell R610 "Unsupported memory configuration" bios message

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This is what Intel calls an "unbalanced" memory configuration.  It is a configuration that technically works and is allowed (you are able to boot and use the system) but can significantly decrease performance (hence the BIOS warning).

It wants all channels to be populated evenly - not so much the amount of installed RAM, but the number of installed modules.  Populating slot 3 but leaving slot 8 empty creates an unbalanced configuration across the channels.

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theflash1932
6 Indium

Re: Dell R610 "Unsupported memory configuration" bios message

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This is what Intel calls an "unbalanced" memory configuration.  It is a configuration that technically works and is allowed (you are able to boot and use the system) but can significantly decrease performance (hence the BIOS warning).

It wants all channels to be populated evenly - not so much the amount of installed RAM, but the number of installed modules.  Populating slot 3 but leaving slot 8 empty creates an unbalanced configuration across the channels.

lsdejones
1 Copper

Re: Dell R610 "Unsupported memory configuration" bios message

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Thanks for the explanation. The dell manuals really were no help.

This leads me to the following questions:

1. How can I change the configuration so that I get a "balanced" config? I don't completely understand what you mean when you talk about slot 3 and slot 8. The only slots empty now are the end slots. (have all slots filled with 2G sticks? ... or buy another two 8G sticks? ...  or ?)

2. What  are the performance decreases? ... seems like all it is really doing is stopping the server from running in tri-channel mode. i.e. it cant triple up on the bank usage and has to use the memory in a linear fashion ... which I guess would 1/3 the memory bandwidth (?)

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theflash1932
6 Indium

Re: Dell R610 "Unsupported memory configuration" bios message

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1. Sorry, I meant 3 and 6 (not 😎 ... the slots are numbered 1 4 2 5 3 6 and must be populated by smallest number first, so with 5 DIMM's, you did right to leave only slot 6 unpopulated, but populating 3 and not 6 is what is causing the unbalanced configuration.

I realize the Dell docs weren't very helpful with this ... most of the servers contain a phrase similar to "all POPULATED channels must have identical configurations", which to some sounds like they must all have the same size, number, speed, etc., but it really just is referring to Intel's configuration recommendations to populate the channels with the same number of DIMM's for optimal performance.  For some reason this phrase is missing from the R610.

My recommendation would be to get another 8GB DIMM for slot 6, as it is the easiest fix without decreasing the available RAM.

2. Your thinking is pretty spot on ... I think I remember reading between 23-28% performance decrease in such a configuration.

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KevinNoall
1 Copper

Re: Dell R610 "Unsupported memory configuration" bios message

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I hope i'm not too late to the party and someone will see this...

I just put some additional RAM in my R610 and I'm getting this message, although I dont understand why. Here is my config:

A1(16g) A2(16g) A3(16g) A4(16g) A5(8g) A6(8g) - B1(16g) B2(16g) B3(16g) B4(16g) B5(8g) B6(8g)

The system is reporting the 160 total, but says that A/B 4,5,6 are mismatched.

Is this because of size or?

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lsdejones
1 Copper

Re: Dell R610 "Unsupported memory configuration" bios message

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It because the memory you added is mismatched to whats already in the server.

For the R610 to be in "optimal" configuration, not show that error message, and get through POST without prompting F1 to continue, all of the ram sticks need to be the EXACTLY the same.

Same size, same speed, same latency, same number of chips per side, matching rows and columns etc.

What is really going on, once you read through the fine print, is that the "optimal" memory configuration for the R610 is the same as a home PC's "dual channel" memory mode. I.e. the two memory banks both run in parallel to effectively double the ram bandwidth. However dual channel only works if all your memory is the same.

So you have three choices:

1. Take back your RAM and get stuff that is the same as whats currently in your server.

2. Ditch the servers current RAM, and buy 12 new sticks that are all exactly the same, from the same manufacturer, and put those in.

3. Tell the BIOS to ignore F1 to continue POST error messages, and just accept that your memory bandwidth will be a little lower. <--- This is what I did. (Haven't noticed a difference in performance except in memory bandwidth tests ... meh).

As for why Dell decided that non optimal memory configurations should be considered critical enough to stop the server from getting through POST?

... Well I can only assume they are massive idiots. emoticon.Indifferent.title

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KevinNoall
1 Copper

Re: Dell R610 "Unsupported memory configuration" bios message

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Interesting, thats what I was thinking about the mismatched sizes.  

I do not get a POST error, and i dont have to F1 to continue, so I'm not sure that this is a huge error. I'm mostly concerned if there will be a performance issue, and how if/and or how I would be able to tell?

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lsdejones
1 Copper

Re: Dell R610 "Unsupported memory configuration" bios message

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It could be that you have a different BIOS version than mine. That would explain why you did not get the F1 to continue.

Yes there *could* be a performance decrease.

Eg. in optimal mode you may get memory transfer rates around 1 Gig / sec (i am making these numbers up), however in non optimal mode you may only get rates around 750m /sec.

Will this impact you? depends what your server is doing, what sort of loads it carries, etc etc etc.

How can you tell? run benchmarks or load tests on the system to see if there is any difference in performance between configurations.

Whats the catch? well the server may actually perform better with more ram running at a slower rate than with less ram at a higher rate.

TL;DR : depends. Run simulated load tests on either configuration to be sure.

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KenByrd
1 Copper

Re: Dell R610 "Unsupported memory configuration" bios message

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I get the post error.  I have 4 X 2 gig sticks for 8 gigs of RAM.  I populated A1, A4, B4, B1 as I thought the chart said but I get the F! thing.  The Dell charts don't really make much sense.  I wish someone could just tell me how to install 4 X 2 gigs of RAM.  Thanks!

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lsdejones
1 Copper

Re: Dell R610 "Unsupported memory configuration" bios message

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Probably should be A1,A2 and B1, B2. (just guessing)

Do all sticks the same technical specs?

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