Is there a method of calculating exactly how much dictionary space is available per bus or plug-in slot?
Dictionary space is not allocated per bus or slot, it is one large pool which is consumed on a “as probed” basis. If your card is the only one in the system and you are running out of dictionary space then there is a major problem with the board/FCode. However, if your card is one of the last to be probed, then it’s possible that other cards are consuming “normal” amounts of the dictionary and that your card is just trying to get a little more than is left over. It is also possible that the FCode on your card could be written inefficiently such that you could reduce its dictionary space requirements by some margin.