RPi 3B+ Core & GPU (V3D) overclock - is it still possible?

[dilbodoop]

Dear forum users.

First to say, I love the community here and I've been lurking for some time now here. My question is on the state of overclocking the GPU on 3B+.

In short: I recently migrated my 3B+ board (in MegaPi case with 3.2A supply) from RetroPie 4.5.1 to 4.7.1. Clean install using Win32DI/Etcher then a full system update (I also skipped update in iteration #2 of troubleshooting to avoid updated kernel and use standard build; didn't help with this issue) after which I ported some of my ROM's, did the scraping etc.

After setting up safe shutdown and everything else, I went into finetuning the oveclock settings. After copy-pasting my custom settings from previous config.txt that worked for 2 years on that same board/sd card (core_freq = 550 and some slight overvolting), I noticed the system would freeze shortly after the boot. After lots of troubleshooting, I found the issue is belonging to any overclock setting related to GPU or Core speeds (even 5-20 MHZ increment). Everything else would work fine.

After looking around, I found some Github comments and a few sporadic posts referencing DVFS-related changes implemented in the firmware commit around November 2019 that apparently broke overclocking capabilities for 3B+ among others but should not officially because by documentation, DVFS is sort of Pi4-only thing. However, it seems it kind of went under radar as no one is really pointing it out in the documentation and I couldn't find any sort of official reference that overclocking GPU settings doesn't work anymore in RPi3B+. To rule out a change in 3B+ firmware only, I tested also with another board, a 3B model and found the same issue on RetroPie 4.7.1.

So to check here, did anyone encounter this and is there still a way Core/GPU overclock is possible on pre RPi4 models, namely 3b+ on Retropie vesions above 4.5.1 (including 4.7.1)? If it is, can you please tell me if you found a way and share how to do it? I am starting to think I am overlooking some super simple thing.

For those suggesting to restore backup - dd botched my backup (maybe forgot to sync buffers or something) so going back to 4.5.1 is not an option (and I couldn't find old official images anywhere).

As far as troubleshooting to determine the issue: I played with core_freq, gpu_freq, v3d_freq directly, with and without easy overvolting, sizing up the gpu_mem accordingly and all combinations in between. arm_freq and other OC/parameter settings in config.txt worked like a charm still. Also used two SD cards and two PI3 boards.

Thank you all for your time and ideas!