On Tue, 30 Jul 2019 13:26:37 -0400, Paul wrote:

Why extra cable load compensates for a motherboard flaw, is the mystery.
Maybe you just need the right stuff.

You'd need to compare two motherboards using the same
chipset, in the IDE connector area or next to the
Southbridge, to see what corners were cut to save
a few pennies. There is undoubtedly an explanation.

My opening post referenced

https://forums.tomshardware.com/thre...v266ad.435007/

which archived alt.comp.periphs.mainboard.elitegroup, where Tim said:

I have a K7VTA3 6.0 here and it has different SMC resistors (more of
them and different values) along the IDE port traces than M811 3.1,
which I suspect were to correct the very problem in question.


Some chipsets use a single "reference" resistor to set
the slew rate on pad drivers, and an incorrect value
there could affect the waveform.

Yes an M811 engineering error. So many years without an easy workaround.
And now, who cares. That's OK. I still use the board, so it helps me.