RAM speed limited on certain slots

[Turbof1]

I today ran into an issue that feels... odd. I have an Asus strix B550 A-Gaming coupled with a ryzen 5 5600x. The ram slots from left to right are called B1, B2, A1, A2. B1 & A1 and B2 & A2 are the 2 dual channel set ups.

Previously I had a G-skill Trident Z 2x8GB 3000mhz kit. The DIMM's were put in B1 and A2. DOCP never worked but since I was able to manually set the RAM speed at 3000mhz I did not gave it much thought.

 

Today I received a G-skill Trident Z Royal  2x8GB 3600Mhz kit. I replaced my previous kit with this in the same B1 and A1 slots. This booted normally at the default 2133mhz speed. I tried again to turn on DOCP, pc would not post with this and returned to default 2133mhz.

So tried to set it manually to 3600mhz. Again no post and defaulted back to 2133mhz. I then tried several things, like updating the bios and setting the timings and voltage manually. Again no luck at 3600mhz.

 

I then took a more gradual approach. Since it would atleast post at the default 2133mhz, it should not just be a hardware malfunction. I gradually upped the RAM speed going from 2133mhz, each time getting a post. The max speed with it posting was 3133mhz. At 3200Mhz it would not post. I was kind of a bit frustrated by this, as the ram kit is 3600mhz and I did want that performance. I took the manual to see if I overlooked something. The manual refers for single dim te be installed in B2, and a 2 DIMM kit in B2 and A2. Only if 4DIMMs are at play, it would refer to using B1 and A1. I did notice this before when I just got the board, but I figured this was only because a big cooler could impede RAM clearance for slot B1.Since my cooler does not tower over the slot, I put the dimm's in B1 and A1 at the time.

 

I then switched my modules from B1&A1 to B2&A2. And this worked: the ram speed is sitting perfectly fine at 3600mhz.

It leaves me a bit confused, since nowhere in the manual it refers to B1&A1 to be the "inferior dual channel" setup. Is this normal, or is there an issue at play?

[Guest]

That's because for dual channel, the populated slots are supposed to be A2 and B2. Should note that in the manual with a little picture even.

[--SID--]

Also depends on the MIC on the sticks. What MIC is on the old and new sticks according to Taiphoon Burner?

[Turbof1]

30 minutes ago, Guest 5150 said:

That's because for dual channel, the populated slots are supposed to be A2 and B2. Should note that in the manual with a little picture even.

Yes, but A1 and B1 are also intended for dual channel. Nothing contradicts this and the bios will even tell you if you misplaced dimms, which it did not for that setup.

[Turbof1]

19 minutes ago, --SID-- said:

Also depends on the MIC on the sticks. What MIC is on the old and new sticks according to Taiphoon Burner?

You will have to explain that one because I have absolutely no clue what MIC is for RAM.

[Guest]

8 minutes ago, Turbof1 said:

Yes, but A1 and B1 are also intended for dual channel. Nothing contradicts this and the bios will even tell you if you misplaced dimms, which it did not for that setup.

No, the manual says nothing about A1 and B1 being the primary dual channel slots, because they are not primary dual channel slots. Board manufacturers haven't used A1 and B1 for dual channel since DDR3 systems. 

 

A1 and B1 are secondary slots for additional memory which would still be in dual channnel.

 

A2 is also the Single Channel primary slot.

 

WHY they don't say the reasoning is beyond be. But above is how the boards are designed by default ALL manufacturers. 

[--SID--]

44 minutes ago, Turbof1 said:

You will have to explain that one because I have absolutely no clue what MIC is for RAM.

It's the memory IC, the memory chips that are on the sticks. Not all memory ICs are working properly with Intel and AMD.