Question Unable to post at XMP Speeds

Jul 13, 2021
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Having some trouble getting my pc to boot with the correct ram speeds. Trying to install 32 GB of G Skill Trident Z RGB DDR4 4133 into my Asus Prime X570-P. This is 4 sticks of 8 GB each. My desire is to underclock this ram to 4000 and run FCLK at 2000.

Installing the ram into slots 2 and 4 (the correct slots for 2 sticks) I am able to boot into Windows with any combination of the 4 sticks all the way up to 4400 at 1.4v and auto timings. Installing the ram into slots 1 and 3, I am unable to post at anything above 3400. With all 4 sticks in, I am able to get to Windows at 3600. Above 3400 using 2 sticks in 1 and 3 will result the pc restarting 3 times during boot, then prompting me to enter bios due to a failed post and in bios the ram will be at 2133. I get the same result with all 4 sticks above 3600. Like I said, any combination of the 4 sticks works fine all the way up to 4400 as long as I am using slots 2 and 4. Is this board incapable of handling 4 sticks at 4000 or is there some other setting I need to adjust?

Rest of the system: Ryzen 9 5900x, EVGA 3080 XC3 Ultra, 800W 80+ Gold PSU

TIA
 
Jul 13, 2021
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Page 1-5 of your manual (I tried to copy/paste) states that installed memory may not reach advertised speed with all four slots occupied.

E17441_PRIME_X570-P_UM_v3_WEB.pdf (asus.com)

I was looking in there for the chart that is sometimes in the manual which will show supported RAM speed based on slot population but did not see that in a quick look.
Is it the line that says "The default memory operation frequency is dependent on it Serial Presence Detect (SPD), which is the standard way of accessing information from a memory module. Under the default state, some memory modules for overclocking may operate at a lower frequency than the vendor-marked value"? I'm no expert, but I read this line as "if you leave things at default, they won't run at advertised speeds" and default would be 2133 or whatever. XMP is importing the correct "overclocked" values; I don't see anything about 4 slots making a difference other than the line about using a more efficient memory cooling system (unless that line means the memory cooling on this board is insufficient?)
 

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