I hate to break it to you but the computer I had in the 80s didn't come with ECC. Non-ECC computing was a thing WELL BEFORE Intel tried to think of market segmentation. Revisionist history is not welcomed here.
The DDR4 ECC RAM has 72 bits total and 64bits of data which means the same 9/8 ratio of data storage to usable data as the original PC/XT.
The Z80 and 6502 based computers in the 80s typically didn't have parity RAM. The Amiga and Macintosh were higher performance systems in the 80s which also didn't have parity RAM.
We could and should have gone straight from parity RAM to ECC RAM for everything.
Absolutely all IBM PC originals or clones until those with 486 and with the early Pentium variants supported parity on the motherboard.
The user could choose to not install the parity chip (or when the first memory modules appeared there were also slightly cheaper modules without the parity chip), but that was the user's decision, all the motherboards supported parity.
On IBM PC compatibles, the lack of protection against memory errors had never existed before Intel segmented the market between "non-Pro" and "Pro", by launching the Triton chipset, which no longer supported parity memory.
As long as the memory modules were byte-wide, only parity could be implemented. ECC memory could appear only later, after the passage to wide memory modules.