DMA Beast

[Dennis Conley]

Hi. I'm tasked with moving a Vector General 3400 from a pdp 11/55 running
V7 to our 780 running BSD 4.2.  This machine uses dma to access a 
user-generated display list in memory, and has a history of rude behavior 
( i.e. write operations to memory locations belonging to other users, the 
kernel, etc ). It seems that the move is a forgone conclusion, and I must 
attempt to minimize any potential damage to other devices/processes that 
it will try to cause via the unibus adapter on the vax. My queston is, to
what extent is 'protection' from such illegal access possible via the 
UBA ( or other ) hardware or from the kernel? I've yet to grok in fullness 
just how the hardware and the kernel deal with this topic, if at all. 

Thanks much, direct replies would be appreciated.

	Dennis R. Conley
	Computer Science Dept.
	University of Kansas
	conley%ukans.csnet