[Simh] More on DMA to IO page

[Johnny Billquist]

On 2018-09-07 00:38, Eric Smith wrote:
> On Thu, Sep 6, 2018 at 4:31 PM, Johnny Billquist <bqt at softjar.se 
> <mailto:bqt at softjar.se>> wrote:
> 
>     Well, you'd probably also need to deal with the Unibus map handling,
>     since those addresses also do not generate accesses directly on the
>     memory bus...
> 
> 
> Really? What's the highest physical address the Unibus map supports?

Uh? The Unibus map is for translating 18-bit addresses to 22-bit 
addresses. And it can translate all of it. In fact, you can (at least in 
theory) go a bit above 22 bits that way.

If you look at the physical address space of the 11/70 however, the low 
3840 bytes are doing on to the memory bus. 3840 to 4088 is going to the 
Unibus memory space, which is remapped by the Unibus map, if enabled. 
And the last 8K goes to the Unibus.

   Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol