Thank you again! I'm not sure I can manage to mod the board and I do feel I should give up on the older cpus eventually. The obsession is that I have 3 kids who all like to play, so I'm actually trying to keep parts going as long as I can to keep the total number of working pcs up. My plan was to use this and the i5-6600k, to give me 3 ok machines (the other being a ryzen 5 5600x) and then build a new one around a 7800x3d or 9800x3d lol.Is it any more stable if you disable the Turbo and cull a few hundred Mhz from it?
If you can get it generally stable, where it doesn't produce any errors, then I guess I'd consider keeping it.
But, really I'd suggest you open a claim and return it, because if they're so confident that it works why don't they just take it back? That marketplace almost always side with the buyer anyhow.
If it was me, I'd consider something like this (or the 5600/5600X, as you said), rather than faffing about with these old CPUs:
My basket at OcUK:
- 1 x Intel Core i3-12100F 3.30GHz (Alder Lake) Socket LGA1700 Processor - Retail (SKU: CP-6AS-IN) = £73.99
- 1 x MSI PRO H610M-E DDR4 (LGA 1700) DDR4 mATX Motherboard (SKU: MOT-MSI-03383) = £59.99
Total: £133.98 (includes delivery: £0.00)
You could likely pick up a 6700K cheaper too, if you prefer, though 6th gen has a higher performance hit from the security features being enabled if you upgrade to Windows 11.
Another thing of note: most boards can be modded to support 8th / 9th gen CPUs if you really want to hang onto it, but don't know if you're into that.
So this fault messes me up.
I can't get that core stable if I under clock either. But prime95 will run fore hours, so long as I stop the worker using that core.
Does that i3 get me into win11 territory?

Anyway it certainly proves I shouldn't push the button and spend MORE on a second i7-7700k!