X570 Steel Legend don't boot dual channel memory

Hello There,

My config
Motherboard: ASRock X570 Steel Legend
Processor: AMD Ryzen 9 3900 X
RAM: HyperX Predator 2*16 GB Kit - HX432C16PB3K2/32
Power suply: FSP Hyper M85+ 650W
Bios version: 2.30
Operating System: Windows 10 64-bit Pro

Power cable connection: Tried two configs
1. 4-pin in ATX12V1 and 4-pin in ATX12V2
2. 8-pin in ATX12V1 and ATX12V2 not connected.

When I put the two RAM modules in A2/B2 slots the PC resets 3 times and after that it can POST successfully (with fallback default config).
Before enterning bios there is an error message visible on the screen:
Memory PMU training error at socket 0 channel 0 DIMM 1
When I enter bios, on the main page only RAM in A2 slot tells 16 GB, DIMM B2 sias none. This is the case for default UEFI settings and for XMP profile also (tried both XMP-3000 and XMP-3200). However in OC Tweaking under DRAM Information both RAM modules are visible in slot #3 and slot #4, with different serial numbers. Also CPU-Z (in Windows) can see both modules and a total size of 32 GB.

I am able to boot with 2 RAM modules in A1/A2 with default bios config (DDR-2400) and also XMP-3000 and XMP-3200 works fine.

With a single RAM module in B1 or B2 the PC won't POST, unable to reach bios. (I cleared CMOS every time I changed the RAM placement)

Do I need to connect all 12 pins of ATX12V1 and ATX12V2 connectors?

(This section of the user manual is quite ambiguous in my opinion. A detailed explanation of the different powercable connection options and their effect would be helpful.)

What further config may I try?

According to the datasheets I consulted my RAM kit is in the QVL Matisse list, also the Ryzen 9 3900X should be compatible.

What am I missing here? I started to think that my motherboard is damaged somehow and I am struggling in vain here. If that is the case is there a way I can get proof of that?

Any help would be appreciated. I am troubleshooting this issue for way too long now. (on the expense of work time in the solitary of home office quarantine)

Best regards,
Balint

You need to plug the 8 pin. Generally, connecting 8 pin is enough, this provides 235W of additional power (some also comes from the 24 pin). Additional 4 pin is excessive on AM4 and can be ignored.
650W should be sufficient with a low to mid-end GPU. If you have a 250W+ GPU (even if it's an old one), you will probably need 750+W PSU.

Is there a reason for you to suspect the board is damaged? Did you buy it used or something?

I guess these are dual rank sticks which is harder for the memory controller to drive.
Make sure you enable Gear Down mode and disable Power Down in memory settings.
Then you can try 2T command rate instead of 1T.
Then try running them at lower speed, like 2933 MT/s, or play with voltage and timings: try running with 1.4-1.45v, or increase tRCDRD a couple of ticks.

I tried Gear Down mode enabled and Power Down disabled, command rate at 2T.

Tried with XMP profile 3200, and default 2400 MT/s with default timings, and also increased tCAS, tRAS, tRCDRD, tRCDWR.

All configs had same effects. POST fails, then reset, this happens 3 times, then the PC boots with default BIOS config.

I am loosing hope here. Thanks anyways.

I updated the BOIS to 2.60. I see a new menu point in OC Tweaking called DRAM Profile. But that seems to be for Corsair RAMs only.

However I gave it a shot anyway at 3200 MHz. Also 2400 MHz and 3200 MHz with XMP profile.

Still no luck, same effect with the 3 times resets then default settings.