I'm the Original Poster, and I have an update.
Now that 2503 is no longer listed as a BETA firmware I thought I'd take a fresh look at this.
I did not re-download the firmware just because its not listed as BETA. I take it that if there had been a change they would have given it a new version.
I reapplied the optimised defaults (which I thought I had done) and reapplied just XMPII for my memory, and tested again, and this time it has been thoroughly stable. P95 [torture, with threading, all cores, all AVX left enabled] 30 minutes Large FFTs, 15 small, 15 minutes medium, 30 minutes blend. Cinebench R23 30 minutes. All stable, no errors, no windows hardware error flags (such as monitored by HW monitor).
Now, there is a possibility that this difference is that I'm not any more stipulating an AVX guardband scale factor of 100, but I doubt I reapplied that when I tried to go back to defaults + XMPII. The other change I made was to change VRM Loadline to from 4 to Auto (not the default) and back to Level 4 (which is now the Asus default).
The other possibility is that this was some exotic windows bug (would have to be pretty exotic, assuming you don't count the whole downgrade of user experience that is W11 as one gigantic bug ), the other thing is that I gather Microcode updates can be delivered by windows sometimes? Has something like this happened?
I have even been able to reapply my Global adaptive undervolt of -0.052 (tuned to my chip) during the above tests.
So basically my QVL memory is once again operating stable with its supplied XMPII profile with defaults.
To anyone out there still having problems I feel for you. This whole microcode change has thrown tings in the air.
In an ideal world (while I appreciate that Intel has created a huge burden/cost on the mobo makers), I would like more detail from ASUS, on whether they have rerun their QVL tests in light of the 0x129 change. But I sympathize if they have not (unless intel is going to foot their bill), and I sympathize that they have not jumped at the chance to highlight this as people will blame them, when they should be blaming intel only.
(SALTY OPINION: To be honest I'm thoroughly disappointed with my experience of enthusiast PC building in many respects not just this intel business. The cost vs features of the motherboards, the poor experience overall I regret I've had with this ASUS Strix Z790E board given the price I paid, the cost of GPUs now.
Concerning Mobos, I just want a Z790 board, premium price quality/longetvity of components, with a diagnostic display. I don't need 3/4 of the 'features' this board has.I would would have 'preferred' that it did not have such 'convolutions'. That said I was content until I realised that the ASUS crate software is horrendous junk, and I now can't even use half of that 1/4 of features. It does not work. And causes no end of headaches beyond the software own features. Then there is the whole business of the 'custom' ergo 'in'secure boot 'un'protection configuration and the dismal rootkit approach to forcing ASUS crate from the UEFI bios. That's a horrific practice. Especially when you look at the state of ASUS crate. It seems to be built on JSNode:- for software with elevated privileges, rootkitting itself from firmware, with access to kinds of BIOS settings it has... the mind boggles. JSNode has its place, but it is not for something like this.
As far as I am concerned enthusiast PC building is now just a badge of shame. Its a 'mug's game'. Unless you've got no-choice/no-life for some reason like me, buy a console [best value GPU on the market] and get everyday driver laptop with an i5 or something there about.$500 for a console. How much does a PC cost? By not buying one what's the earliest you can now update you console and be ahead on savings? Answer, as soon as the next one comes out. You could replace a PS5 with a Pro and not give it a thought.
Enthusiast PCs are now an foolish game. My old Gen 2 i7 with the ASUS P9Z68 board back then was absolutely knockout. I was proud of that machine for 11 years, the mobo in particular. What the goodness gracious happened.)
