Do try OrgAMS (that does use extended RAM and 3 ROM), shall be so cool.
==== Analyse ====
Actually I do use only A(22..0) of external RAM (I'm using them for 64KB ROM + 128KB RAM + 178KB DSK), and MiST-board has A(24..0), so I have at minimum... 64+128+178=370<512KB *2*2 -1 so I have... around 512KB+1024KB free ?
2^24=16777216 /1024=16384KB normaly ?
So 256*16KB ROM= 4096KB ROM and 64KB lowerROM and 64K BaseRAM and 512KB RAM and 178KB dsk shall do 4914KB<16384KB so in theory it does pass.
Last problem is saying "here no ROM, do read RAM" : it does make a mask of 256 bits, why not. I have also to find a way to attach rom name to placements, I think that a hexa number in extension can be fine, as myRom.R00 to myRom.RFF.
And finally that has to enter in MiST-board plaform at compilation...
== Agile method ==