68300

Okay, the programming of CS6 (as it happens, this was the next open CS) to 
the values that Brian Geery gave ("$FFF8 to CSBAR6 & $6B81 to CSOR6") 
actually worked. I am now getting my interrupt.

I suspect that there is a lot more information in the CSBAR fields that I 
will have to understand deeply. Right now this seems to be JPBM (just plain 
black magic).

Charlie, can you explain why this worked and how to properly configure a 
chip select for AVEC/DSACK generation?

Thanks again,
Andrei