> 3. The Q-bus comes in 2 (or 3?) flavors, the original with 18 bit addresses,$
I wouldn't go that far. I would say the MicroVAX-II counts as "in the Qbus world", and it has hardware to map Qbus memory space accesses to memory accesses, rather like the Unibus Map you sketch. DMA is "always to the memory address specified" only if you never look past the Qbus view of the world; from the CPU's point of view, Qbus DMA addresses get remapped before hitting memory. /~\ The ASCII Mouse \ / Ribbon Campaign X Against HTML mo...@rodents-montreal.org / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B
