elianda wrote:Ok, so having the Emu8K directly accessible through 0x620 and providing general MPU-401 access to it through e.g. a MC68K would not be possible at the same time?
As mentioned, the biggest problem is Creative's apparent disdain for the hobbyist community, in general. Apparently, they would rather get no money at all for their legacy chips, than a little, by providing low-cost documentation and a reasonable, low-volume unit price. There have been a few accounts of people trying to contact them about such projects and not getting any response.
Creative arrogance aside, I suspect that an implementation like you describe would be possible, if somewhat inelegant. It would involve carefully considering the compromises you would be willing to make, altering the board design, then a fairly significant development and testing effort for the firmware, especially if you want SoundFont support in both modes. Even then, given the level of integration of the chip being used, there is no guarantee that there wouldn't be any unintended side-effects due to the change in design.
Basically, it would be a non-trivial effort, with a certain possibility that you get nothing in return. Given that they have already said that this will be a low-volume, high-cost project, I doubt it would provide a reasonable return on investment or development effort.