25 Jan
2012
25 Jan
'12
7:49 p.m.
On Jan 25, 2012, at 2:03 PM, Holm Tiffe wrote:
Aha. So it is haindled differently under program control as in the ODT Mode.
That was my question.
Yes, it has to be; the PDP-11 is a 16-bit processor, so those extra two bits have to come
from the MMU. In my experience with my KDF11, 773000 is interpreted differently from
173000 by ODT. As far as the CPU's execution unit is concerned, though, they're
the same.
- Dave
ODT only knows 16bit octal. And BBS-7 is activated
when the upper three
address bits are active for addresses greater than 160000 which is IO
and boot address space.
Not quiet, on a KDF11-A ODT is 18-bit. Under program control, the CPU
uses BBS7 to address the I/O page regardless of high-order address bits.