One mystery to me was why did the industry stick with the EIA-232 levels
for terminals and whatnot long after differential EIA-422 was
introduced.  Higher-speed, better noise immunity, single-ended power
supply...  Seems that the popular places were Appletalk and ST506 data
lines.  But not on DTE/DCE.   If you were using full-voltage (±15-±25)
at high speeds (>500Kbps), the slew rates were ridiculous.

Inertia?  My old 80286 motherboard had junper-selectable 232 or 422.

Still have a couple of tubes of 422 drivers/receivers.

--Chuck

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