Question for DDR3 RAM on DIMM

[Nguyenvanhieu]

I learned layout for RAM, both Fly by and T Branch topology. But I have a problem about compatible between RAM on DIMM and motherboard. What information I need to know (about RAM or motherboard) if I want my computer will work perfectly after I plug in RAM into motherboard ? Is every RAM on DIMM compatible with motherboard without any change in firmware or OS of motherboard?
I remember you say about this somewhere but I can not find.
Thank you

[robertferanec]

• First, be sure the memory controller supports connection through socket. In some design guides they do not mention connections with sockets or they even say it is not recommended. Ideally you may want to see in datasheet, that they support DIMM / SO-DIMM memory or at least you would like to get confirmation from the chip manufacturer.
• Once you design a board with a socket, you should be able to use any memory module, but in reality it may not be always truth. Test several modules and use the manufacturer which works the best and reliably.
• Be sure you follow design recommendations when connected CPU with the socket. Usually there are some length matching recommendations and restrictions. Check out Design guide of the processor and have a look at the reference design.
• As you know, you may want to run DDR3 calibration. I am not sure what type of CPU you use, in x86 BIOS handles this, but if you use a different architecture you may want to think about it.

[Nguyenvanhieu]

Hi robertferanec ,
I want to ask if I route DDR3 RAM on DIMM by T-branch topology instead of Fly-by , Do I need to run to cablibrate my RAM for specific processor?

[robertferanec]

For DDR3 you always need to run calibration, also for T-branch topology - that's what we do.

[Nguyenvanhieu]

Hi Robert, I read your post in blog http://www.fedevel.com/welldoneblog/...ng-a-software/ . But this post mention for RAM on development board.If I have a RAM on DIMM and it will be plugged into motherboard of a laptop and I need to run calibration this RAM.How can I do?

[robertferanec]

BIOS should do it automatically.

[Nguyenvanhieu]

I want to ask the last question for this topic. Can I plug into motherboard slot different type of DDR RAM(same DDR3 type) DIMM ,for example RAM type 256x16 and 512x8?or RAMs have 2 type :bus 1333 and bus 1600?
Thank you for all your answers.

[robertferanec]

DIMM modules are often manufactured with different chips - it doesn't really matter if they are x16 or x8 .. it only changes number of chips placed on the module. Usually, when you can plug it in, it should be compatible, but no guarantee (of course, you may want to use a module supporting same or higher frequency as your chipset does)

[Nguyenvanhieu]

I got it. Thank you