Btw, in a spanish forum, we're trying to clone the EXDOS controller: Controladora de disco para Enterprise
It's only in spanish, sorry. Also, the forum engine is a bit retrictive and links are not shown to unregistered users 
; but I'll be happy to give you all details about the development.
Why not talk about it some months earlier?
It is looks as creating full clone of the original card. But it is can be optimized for a less components!
Firstly see the
floppy part of the MICROTEAM card. It is (and all other hungarian clones) using 2 7406 instead 3 7438.
It is use 74LS245 instead 74LS126 because the 245 ICS are more common.
And the main problem with the original card: it is developed for a "Plug and Play" bus system, where the bus sockets have a extra socket address pins, and these are also used for memory and I/O address decoding. Each slot have a different address space.
But this system never released, because the Enterprise company crashed
Only the one socket System Bus Bridge and the original EXDOS card used this complex address decoding method.
All other expansion and EXDOS clones used a fixed address decoding for a less components.
For a build new EXDOS clone I also suggest fixed decoding.
For a ROM I suggest a 512K Flash ROM IC, it is can be filled with lot of programs
and optionaly can be added 512K SRAM chips as RAM expansion, because easy to do it
For 512K ROM chip + X*512K SRAM only needed ONE 74HCT138 as address decoder!
And I think another two chips enought for the I/O decoding.
