I added a delay so that the current byte would finish before the write is ended and then the crc was written correctly. I still got an error though because the verify read was interrupted before the crc was read. Seems to me that if a read or write are interrupted it should complete the current sector like the 765 does. I have no machine with a wd1790 to try it on though.
would it be possible to see the code you added for that?
Well it would seem that the Nimbus relies on this behavior, and it does seem to work this way on the actual hardware, as I've not seen the same problem at all.