MP 6,1 2013 Mac Pro does not recognise RAM in slot 1

[macguru9999]

I have posted about this before but I think this present title is more to the point. I have a 2013 Mac Pro does not recognise RAM in slot 1.
It came to me as a 4core with 4x8g ram that was always shutting down & restarting. esp when testing ram, it did not always recognise all the ram but i think the chips are ok. I have ordered more to verify. slot 1 did not work with any of the 4 chips.
Yesterday I cleaned the mac inside and installed a 12core processor. All clean, new paste, screws tight...So far stable no crashes or shutdowns and the geekbench multi has of course about doubled. BUT slot1 still does not work. any ideas ? it does not seem damaged but ... I will probably leave it here however if anyone has any ideas I would love to hear them ! ps/The mac had never been pulled apart before in my opinion and the cpu socket looked good.

 

[macguru9999]

Its the motherboard/ramriser card thats at fault, I am just going to have to replace it and then it will be a 12core/64g model, since i already have a 12core cpu. I really cant say I like the funky engineering, but maybe it will make a good novelty item, like a cube, and in all fairness it outscores my everyday machine (Specs below)

 

[KeesMacPro]

I really cant say I like the funky engineering, but maybe it will make a good novelty item, like a cube

What a shame it's the MoBo, an expensive replacement!
Comparing the 6,1 to the 5,1 i agree with you:
The way the cMP is constructed seems a clear invitation to upgrade/replace/modify the internal parts...

 

[macguru9999]

OK just an update on this issue. I replaced the ram/riser board and now have a full working trashcan !
trying to decide if I should make it my daily driver or keep the 2012 until I am ready to go from Mojave to Big Sur ; 2013 specs are:
64GB Ram
2.7Ghz 12 core CPU
2TB OWC Aura nvme SSD