Question Memory question: 1R/2R

[Leptir]

I'm looking at the MSI MEG Z790 ACE motherboard and trying to figure out the best memory I should get for it. I need 128GB. So I found the G.SKILL Trident Z5 (32GBx2), model F5-6400J3239G32GX2-TZ5RK, with specs: DDR5-6400 CL32-39-39-102 . I would be using 4 sticks.

OK, so now I'm looking at the motherboard specs and I'm not sure I understand the acronyms:

4x DDR5 UDIMM, Maximum Memory Capacity 128GB
Memory Support 7800+(OC)/ 7600(OC)/ 7400(OC)/ 7200(OC)/ 7000(OC)/ 6800(OC)/ 6600(OC)/ 6400(OC)/ 6200(OC)/ 6000(OC)/ 5800(OC)/ 5600(JEDEC)/ 5400(JEDEC)/ 5200(JEDEC)/ 5000(JEDEC)/ 4800(JEDEC) MHz
Max. overclocking frequency:
• 1DPC 1R Max speed up to 7800+ MHz
• 1DPC 2R Max speed up to 6600+ MHz
• 2DPC 1R Max speed up to 6400+ MHz
• 2DPC 2R Max speed up to 5600+ MHz

So, if I'm reading this correctly, with two DIMMs per channel, I can use 6400 memory that is single rank, or 5600 dual rank. Is that correct? And if it is, how do I find if my memory is single or dual rank? I didn't find anything in the specs on G.SKILL's website.

 

[bill001g]

just a guess but I bet they are dual rank. If you look up the similar parts that run on amd you will find a download link that show all the details. All the kits they sell 2x32 are dual rank. Most other vendor 2x32 kits are also dual rank so there must be some manufacturing limitation.

There are no kits for 128gb so you are going to be on your own getting 2 different 64gb kits to work together.

 

[Leptir]

There are no kits for 128gb so you are going to be on your own getting 2 different 64gb kits to work together.

Why is it a problem to get two identical kits of DDR5 5600 2x32GB?

 

[Lafong]

Why is it a problem to get two identical kits of DDR5 5600 2x32GB?

They are not as "identical" as you would hope.

 

[Doug D Z]

Hi, I don’t know if you solved your problem but I have the exact same memory from G skill. The info you got didn’t extend to 4 dpc 2r. Well, I tried so many combinations with the timings and the best I could do with 128gb…with 4 32gb sticks…is 5000mhz. You have to make sure the 2 in each pair is in alternate slots, ie 2 in slot a2 and b2 are from the same pair. The other 2 in a1 and b1. Check the serial number on you sticks. The pair of 32gb sticks should have consecutive sn’s. My settings:
1) choose “memory try it” option in bios and click 6400 with 32-40-40-120 without asterisk.
2) then choose manual speed at 5000mhz.
3) go down the menu and choose enable max voltage selection from auto.

I tried this and 4800mhz, and I think the 4800mhz is much more stable. 6400mhz only works with one stick of 32gb in slot a2 as your list says. And 5600 mhz works with 2 sticks. Hope this helps.

 

[kerberos_20]

Just a guess but I bet they are dual rank

they should be dual rank now, as there are still manufacturing issues with 32GB single rank modules