2) Plug all the drives into one control cable and
select the drives by
switching a control line on the control cable.
This is how I'd go, but the BIOS will only understand units 0 and 1,
you'll need a device driver for units 2 & 3.
Oh, and you'll need a *real* floppy interface cable, instead of
the butchered IBM-style floppy cable that *every* PC I've seen
has, except for the Zenith Z-150 family.
-dq