Question ASUS ROG STRIX B450-F GAMING - RAM Slots A1+B1 stuck at 2133 MHZ

[ciscogreg]

CPU: AMD Ryzen 3600X
Motherboard: ASUS ROG STRIX B450-F GAMING
RAM: G.SKILL Trident Z RGB (For AMD) 16GB (2 x 8GB) 288-Pin DDR4 SDRAM DDR4 3600 (PC4 28800) Desktop Memory Model F4-3600C18D-16GTZRX
SSD: Inland Premium 1TB SSD 3D NAND M.2 2280 PCIe NVMe 3.0 x4 Internal Solid State Drive
GPU: EVGA GeForce GTX 1060 SC GAMING, ACX 2.0 (Single Fan), 6GB GDDR5, DX12 OSD Support (PXOC), 06G-P4-6163-KR
PSU: EVGA 500W
Chassis: SAMA Tank-RGB Black Dual USB3.0 Steel/ Tempered Glass ATX Mid Tower Gaming Computer Case w/Tempered Glass Panel and 4x Addressable RGB LED Ring Fans Pre-Installed
OS: Windows 10 Home

Hello,
I'm putting together a brand new build for my son with a total of four 8GB RAM sticks for a total of 32GB RAM. This is RGB memory.
The problem is whenever I populate slots A1+B1, the memory will only run at 2133MHZ.
I can only get the memory to run at full 3600MHZ speed if only A2+B2 are populated.

Here are my tests results with various slots populated:
A1+B1 - 2133MHZ
A2+B2 - 3600MHZ
A1+A2+B1+B2 - 2133MHZ

I updated to the latest BIOS and tried playing around with various settings such as enabling DOCP and manually setting the Memory frequency to 3600MHZ, but nothing will make slots A1+B1 run at full 3600MHZ speed.
I understand A2+B2 are noted as the recommended memory channel in the motherboard manual, and I have seen similiar recommendations on this forum to use A2+B2 because they are the "primary channel", but I would like to use a total of four 8GB RAM sticks, for a total of 32 GB.
I check the QVL (supported memory) list on ASUS website and the memory is supported, however it doesn't specify which RAM slots it will work in.

Is this a known limitation of slots A1+B1 in ASUS motherboards?
Has anyone successfully run four sticks of RGB RAM in these boards at full speed?

Update:
I did some testing with my other son's PC which has the same specs except for the motherboard and RAM.
My other son's PC has the following motherboard and RAM, all other specs are identical:
Motherboard: ASUS TUF B450-PLUS GAMING AM4
RAM: TeamGroup T-FORCE VULCAN Z 32GB (2 x 16GB) DDR4-3200 PC4-25600 CL16 Dual Channel Desktop Memory

I noticed that when we moved his memory (currently running at 3200MHZ) from A2+B2 over to A1+B1, his memory also runs at reduced speed - 2400MHZ.
We had the same results with both Teamgroup RAM and G.Skill RAM.
So it seems slots A1+B1 run at reduced speed regardless of the memory type.
Is this a limitation of ASUS motherboards or the AMD Ryzen 3600x CPU?

 

[egda23]

CPU: AMD Ryzen 3600X
Motherboard: ASUS ROG STRIX B450-F GAMING
RAM: G.SKILL Trident Z RGB (For AMD) 16GB (2 x 8GB) 288-Pin DDR4 SDRAM DDR4 3600 (PC4 28800) Desktop Memory Model F4-3600C18D-16GTZRX
SSD: Inland Premium 1TB SSD 3D NAND M.2 2280 PCIe NVMe 3.0 x4 Internal Solid State Drive
GPU: EVGA GeForce GTX 1060 SC GAMING, ACX 2.0 (Single Fan), 6GB GDDR5, DX12 OSD Support (PXOC), 06G-P4-6163-KR
PSU: EVGA 500W
Chassis: SAMA Tank-RGB Black Dual USB3.0 Steel/ Tempered Glass ATX Mid Tower Gaming Computer Case w/Tempered Glass Panel and 4x Addressable RGB LED Ring Fans Pre-Installed
OS: Windows 10 Home

Hello,
I'm putting together a brand new build for my son with a total of four 8GB RAM sticks for a total of 32GB RAM. This is RGB memory.
The problem is whenever I populate slots A1+B1, the memory will only run at 2133MHZ.
I can only get the memory to run at full 3600MHZ speed if only A2+B2 are populated.

Here are my tests results with various slots populated:
A1+B1 - 2133MHZ
A2+B2 - 3600MHZ
A1+A2+B1+B2 - 2133MHZ

I updated to the latest BIOS and tried playing around with various settings such as enabling DOCP and manually setting the Memory frequency to 3600MHZ, but nothing will make slots A1+B1 run at full 3600MHZ speed.
I understand A2+B2 are noted as the recommended memory channel in the motherboard manual, and I have seen similiar recommendations on this forum to use A2+B2 because they are the "primary channel", but I would like to use a total of four 8GB RAM sticks, for a total of 32 GB.
I check the QVL (supported memory) list on ASUS website and the memory is supported, however it doesn't specify which RAM slots it will work in.

Is this a known limitation of slots A1+B1 in ASUS motherboards?
Has anyone successfully run four sticks of RGB RAM in these boards at full speed?

What you have are two kits of two sticks. Each kit is tested to run at max speed, but to different kits together are not.
You should have taken a kit containing 4 sticks, or a 2x16GB kit.
If these kits are new, maybe you can exchange for a 4 sticks kit.

 

[ciscogreg]

What you have are two kits of two sticks. Each kit is tested to run at max speed, but to different kits together are not.
You should have taken a kit containing 4 sticks, or a 2x16GB kit.
If these kits are new, maybe you can exchange for a 4 sticks kit.

Hi Egda23, thanks for your response. I understand your point about buying a kit with 4 sticks, however even if I only use 2 sticks as intended, it will only run at 2133MHZ in slots A1+B1. Why is this?

 

[egda23]

Hi Egda23, thanks for your response. I understand your point about buying a kit with 4 sticks, however even if I only use 2 sticks as intended, it will only run at 2133MHZ in slots A1+B1. Why is this?

Il suspect that in the manual they state that if only 2 sticks are used, they should be in A2 and B2.
If this is not the case, than the MoBo could be faulty

 

[ciscogreg]

Il suspect that in the manual they state that if only 2 sticks are used, they should be in A2 and B2.
If this is not the case, than the MoBo could be faulty

Thats correct, the manual recommends A2 and B2 if you only use 2 sticks. I tested the RAM in my other sons other ASUS TUF motherboard and had the same issue. I also tried a different brand of RAM and same issue, it will run at reduced speed in A1+B1. Is this a limitation of ASUS motherboards or the AMD Rynen 5 3600x CPU?

 

[egda23]

Thats correct, the manual recommends A2 and B2 if you only use 2 sticks. I tested the RAM in my other sons other ASUS TUF motherboard and had the same issue. I also tried a different brand of RAM and same issue, it will run at reduced speed in A1+B1. Is this a limitation of ASUS motherboards or the AMD Rynen 5 3600x CPU?

Frankly, I think this question should be asked on an Asus help forum in order to receive an official answer.
If the motherboard is faulty, it is impossible to determine If the RAM should work at max speed with 4 sticks

 

[CountMike]

Thats correct, the manual recommends A2 and B2 if you only use 2 sticks. I tested the RAM in my other sons other ASUS TUF motherboard and had the same issue. I also tried a different brand of RAM and same issue, it will run at reduced speed in A1+B1. Is this a limitation of ASUS motherboards or the AMD Rynen 5 3600x CPU?

This is your second post about same problem, see my explanation in my post in the other thread. In short, all processors have one memory controller with up to 2 channels, only Server CPUs have more and can handle RAM of different speeds. BIOS is also made to reflect that same configuration and have primary (usually A2 and B2 slots and that's clearly marked in MB manual.