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I know that you should always have the same memory clock speed and in best case even the same manufacturer meaning the same RAM Module. But what happens if you use for example the following setup:

Server with 32 GB Memory

1x 16 GB DDR4 1600 MHz 1x 16 GB DDR4 2100 Mhz

Will one Memory be running with a rate of 2100 MHz or will both be dropped to the lowest MHz aka 1600?

Are there any other reasons besides possible performance loss to not use the given setup?

Even though I know what is recommended, I am highly interested in the possible negative effects.

RayofCommand
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    both should run with the same rate (the lower of both) – Froggiz Nov 25 '15 at 11:34
  • I understand, was the downvote from your side? Any proof that it will run on the lower speed? – RayofCommand Nov 25 '15 at 11:39
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    nop wasn't me, and that s why this downvote without info is stupid, cause if we comment after people thing they ve been downvoted by commentator. As proof i vote up your question. I don't know where i can find info on it, but i made some PC in the past, and it was a rules we learn on RAM – Froggiz Nov 25 '15 at 11:41
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    One possible downside is losing support from the manufacturer if you don't use their recommended RAM modules. – André Borie Nov 25 '15 at 12:05
  • Can you provide a reason why you ***wouldn't*** use like/similar memory DIMMs in a server? It's like asking why you _shouldn't_ stick your tongue in an electrical socket! – ewwhite Nov 25 '15 at 12:16
  • The reason is simple, either you have already old memory which is probably as expensive as better new memory, or a server comes with xx gb memory but this is not what u have or need or the price for faster modules is the same. – RayofCommand Nov 25 '15 at 12:32
  • Or, you can use the same RAM in all slots... – ewwhite Nov 25 '15 at 14:19
  • I am a unaware of a system manufacturer or motherboard that reccomends running different speed ram. – Jim B Nov 25 '15 at 14:25
  • No one said that a manufacturer recommends running different speed or I want to do that. It was my pure curiosity what will happen if I don't follow the recommendation. @ewwhite of course I will run the same ram, that was never a question. I just want to understand what happens if I don't – RayofCommand Nov 25 '15 at 14:49
  • @Froggiz As you already know, downvotes without comment can be assumed to be due to one of the reasons stated in the down arrow hover text. – EEAA Nov 25 '15 at 16:20
  • @EEAA Yup, thank i read about it in the Meta. But as i said, the author might think it has been done by the first commentator. – Froggiz Nov 25 '15 at 16:32
  • @Froggiz Well that's just fine if they want to think that. – EEAA Nov 25 '15 at 17:09

1 Answers1

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When using DRAM modules with different speed rating, the CPU's integrated memory controller will negotiate a common, base speed for both modules.

In the example above, the MC will train the DRAM interface at 1.6G T/s

shodanshok
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