Adding Memory question

[PyroTheWise]

Okay, so I am trying to understand something.   I have the following system:

 

Ryzen 5 3600

MSI B450 Tomahawk Max

16 GB (2x8) G.Skill Ripjaws memory (CL 16) 3200 MHz

 

I have no issues with the memory and they are put in DIMM slots 2/4 as recommended.   I am not at this time wanting to upgrade to 32GB of memory but I see suggestions on the forums that you need to replace the kit in order to keep the XMP profile.

 

This doesn't make sense to me.   If I buy the same exact kit as I previously did (same speed, same manufacturer, same CL) then why shouldn't I be able to put in the memory and keep the XMP.

 

In my mind, you should be able to do this and keep the XMP profile on.   I believe the proper way to accomplish is re-arranging the DIMMS.   The original set of DIMMS would be moved from DIMM slots 2/4 to 1/2 - so those paired DIMMs are in the same bank.   The new kit would then be placed in DIMM slots 3/4.   This will still allow Dual channel of course and it keeps the DIMMs with each set they had.

 

Is there any reason why you can't keep XMP profile on and running at 3200MHz in this situation?   My mohterboard manual suggests that is the proper way to installs the DIMMs for this case.

 

Please advise on your experiences/understanding.

 

 

[boggy77]

i think it doesn't even need to be the same exact model. as long as it's 3200c16, it should work. might have to fiddle with timings and voltages a bit to get it stable, but it should work anyway.

[PyroTheWise]

5 minutes ago, boggy77 said:

i think it doesn't even need to be the same exact model. as long as it's 3200c16, it should work. might have to fiddle with timings and voltages a bit to get it stable, but it should work anyway.

As far as placing the DIMMs into the slots - shouldn't you keep the DIMM kits together in the same bank?

 

[boggy77]

Just now, PyroTheWise said:

As far as placing the DIMMs into the slots - shouldn't you keep the DIMM kits together in the same bank?

 

I think I would keep the in 1/3 and 2/4 each kit. but I'm not an expert. maybe someone else knows better.

 

[PyroTheWise]

1 minute ago, boggy77 said:

I think I would keep the in 1/3 and 2/4 each kit. but I'm not an expert. maybe someone else knows better.

 

This is where I am a little confused.  According to my motherboard manual.   DIMM bank A is slots 1/2 and DIMM bank b is slots 3/4.

 

By keeping kit 1 in 2/4 - you have split them to 2 different banks which enables Dual Channel memory.

 

So when you put the second kit into the system, then you are putting them in 1/3 (since you have the original kit in 2/4).  Now Bank A has 1 DIMM from the previous kit and 1 DIMM from the new kit.  This however has to work together (not Dual channel but single channel within the bank).   So my theory/thinking is that keeping the kits in the same bank would produce the best results due to differences in the silicon lottery between the 2 kits.

 

Does it make sense what I am saying and why?  I understand that I am probably way overthinking this....

[boggy77]

you need kit 1 in 1/3 and kit 2 in 2/4

https://web.archive.org/web/20110929024052/http://www.kingston.com/newtech/MKF_520DDRwhitepaper.pdf

https://en.wikipedia.org/wiki/Multi-channel_memory_architecture

[PyroTheWise]

From the wiki article:

 

         A matched pair of memory modules may usually be placed in the first bank of each channel, and a different-capacity pair of modules in the second bank

 

This is what I am talking about.  The First bank is 1/2 on my motherboard.   The second bank is 3/4.  So what I am tyring to explain is what I just read above.