X570S PG Riptide DRAM issue

**Subject:** X570S PG Riptide - DRAM Voltage Locked at ~1.15V? XMP Fails Across Multiple BIOS Versions and Memory Kits

Hi everyone,

I'm hoping someone has seen this before.

**Hardware**

* ASRock X570S PG Riptide
* Ryzen 9 5900XT
* BIOS versions tested: 2.20, 5.40, 5.50, 5.60, 5.80
* Multiple DDR4 kits tested:

* Kingston HyperX Fury 2?32GB DDR4-3200 CL16
* Corsair Vengeance LPX 2?32GB DDR4-3200 CL16
* Corsair Vengeance LPX 2?8GB DDR4-3600

**Problem**

The board appears to ignore any DRAM voltage setting above JEDEC voltage.

Examples:

* Manual DRAM Voltage = 1.35V ??board still reports ~1.15V
* XMP Profile enabled ??POST fails and memory falls back to JEDEC
* Manual DRAM frequency = 3200 with Auto timings ??boots successfully, but only because timings relax significantly (around CL22) while DRAM voltage remains ~1.15V
* 3600 MT/s can also train with very loose timings, but VDIMM never increases.

The interesting part is that memory frequency changes work, but DRAM voltage does not.

**Voltage readings**

All of the following report essentially the same value:

* BIOS Hardware Monitor: ~1.157V
* AIDA64: 1.152V
* HWiNFO: approximately 1.15V

Changing DRAM Voltage in BIOS from 1.20V to 1.35V (or higher) has no effect on the reported voltage.

**Things I've already tried**

* Cleared CMOS
* Loaded UEFI defaults
* Manually set only DRAM Voltage (left everything else Auto)
* Multiple BIOS versions (2.20 through 5.80)
* Three completely different memory kits
* Single-rank and dual-rank DIMMs
* 64GB and 128GB configurations

Everything behaves identically.

At this point I'm trying to determine whether:

1. this is a known BIOS issue,
2. there is a hidden setting I'm overlooking, or
3. the DRAM voltage regulator on the motherboard may be faulty.

Has anyone experienced something similar on an X570S PG Riptide or another ASRock AM4 board?

Any suggestions would be greatly appreciated.
I sent a support message to asrock about 10 days ago but havent heard back.
Thank you