Even more mysterious than the 7D12/7D13 is the motherboard, which I've hardly ever seen with only four channels of RAM except for ITX.
The 7D12 seems to be a purpose-built CPU for storage. Some boards may not light up the machine if the memory is plugged in full. Only the four outermost channels (CDGH) are available.
Hahaha, the other day at OCP Facebook announced the project called North Dome, which is supposed to be the source of 7D12/7D13.
North Dome is 6 channel as far as i have seen and Docs claim it to be completely compatible with basically all epyc CPUs.
Milan preferred and only validated with 95W SKUs.
I found nothing obvious why those 7D13 CPUs are supposed to just work on North Dome.
Of course that changes should we get a North Dome Biosfile