It all depends on the MOBO. My PowerMate 286 Plus has a DIP switch that allows one to disable the onboard FDD / HDD controller. That then makes it possible to plug in an I/O controller. Which is the case for my system.
Which system are you looking at?
http://cgi.ebay.com.au/251441919471
It does not look like the MOBO is included on stason.org:
http://stason.org/TULARC/pc/motherboards/N/NEC-TECHNOLOGIES-INC-286-POWERMATE-286.html#.UvKm6vldXeQ
Which system are you looking at?
http://cgi.ebay.com.au/251441919471
It does not look like the MOBO is included on stason.org:
http://stason.org/TULARC/pc/motherboards/N/NEC-TECHNOLOGIES-INC-286-POWERMATE-286.html#.UvKm6vldXeQ