I have not attempted to assign either controller ROM to either version of DOS. There is no clear indication of which was first or that either set of DOS ROM's requires a particular Controller ROM. There are only 3 significant differences between the controller ROM's: 1) The checksum byte is just before the 2 vectors at the end of the ROM in rev. A, and the first byte in the ROM in rev. B. 2) There are 2 bytes added beginning at location 140 in the rev. B ROM. 3) There are 24 bytes added beginning at location 880 in the rev. B ROM. The code was recompiled with these changes and there are no signs of patches. All the other differences appear to be the result of address changes from the recompilation.