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How is Dual Channel DDR3 routed to CPU?

idata
Employee
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I will use XEON(R) E3-1200 v3 DRAM Controller on my desktop as an example, I am confused how Dual Channel DDR3 works.

On page 18 "2.1 System Memory Interface" of datasheet, it says: Two channels of DDR3/DDR3L Unbuffered UDIMM with a maximum of two DIMMs per channels.

What I learned is that DDR3 PCB Layout is using fly-by topology, so all data lines from memory ICs are directly connected to CPU, but address/cmd lines are shared by different memory ICs.

For this XEON(R) E3-1200 v3 DRAM Controller, there are 4 memory slots on the motherboard, 2 slots for each channel. I have one memory installed for each channel, totally 2. Since each memory slot are 64-bit wide data bus, and this memory controller is also 64-bit wide, so each memory is directly connected to its own channel of XEON(R) E3-1200 v3 DRAM Controller in this configuration.

But if I use all these 4 slots to add more memory, then for each channel, there are two memory slots connected, my questions is: are these two slots sharing same data lines on PCB? If so, then this is not fly-by topology. If not, then how are these two slots on each channel connected to CPU?

Thank you.

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4 Replies
idata
Employee
518 Views

Hello Shi_wei:

 

 

In regard to your inquiry, we are going to do some research in order to provide the most accurate information we can get about how the Dual Channel DDR3 is routed to the CPU.

 

 

As soon as I get all the details, I will post them on this thread.

 

 

Any questions, please let me know.

 

 

Alberto
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idata
Employee
518 Views

Hello Shi_wei:

 

 

In order to further assist you and to continue with our research, please provide the specific model of the Intel® Xeon processor and also the model of the Intel® chipset and motherboard.

 

Any questions, please let me know.

 

 

Alberto
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idata
Employee
518 Views

Hello Shi_wei:

 

 

I just wanted to check if you saw the information we are requesting on the previous post?

We need that information to better assist you.

Any questions, please let me know.

 

 

Alberto
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ssote
New Contributor II
518 Views

Chanel A and B are separate channels, so when you have two memory sticks in A channel that is one channel.

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