flash (or ide) storage for unibus 11?

Johnny Billquist bqt at update.uu.se
Tue Nov 24 11:47:56 CST 2015

On 2015-11-24 16:55, Mouse wrote:
>> 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.

Well, Paul did talk about the PDP-11 and the Qbus in it's "normal" form.
All VAXen (beyond the uVAX I) use the Qbus only as an I/O bus, while 
memory sits on PMI. So then we're back to the same thing as with the 
Unibus thingy, where DMA have to go through a remapping, since the 
system actually have more address bits than the I/O bus.


More information about the cctech mailing list