Apparently at the moment, most RDIMM DDR5 is EC8 ECC which is 80bit.
And most UDIMM is EC4 ECC which is 72 bit.  I don't believe there is
any requirement for it to be that way.

Oh my goodness sake (;-))

That really takes me back: I learned B on a DPS-8, which used 72-bit double-words.

--dave

-- 
David Collier-Brown,         | Always do right. This will gratify
System Programmer and Author | some people and astonish the rest
davecb@spamcop.net           |              -- Mark Twain