moonpie Unlikely to be a placebo, checked many times.
There were no problems with registers access (Secure Boot was disabled also) — I checked it by setting FMT_TRUNCATE_EN flag, which led to strong banding as with real 6-bit image (Windows & Linux).
Maybe there are registers, that changed after RAM swapping on Intel — we tried to find something valuable in the difference of intel_reg_read results, but with no luck.
I understand your opinion and very appreciate your passion to help. But after many experiments, it remains only to operate with the dry facts, based on our custom experience.
Thank you!
P. S. Just in case will check regs tweak again. Are there any flags from dcn_3_1_4.reg and another files to check? I played with regFMT* primarily.