18 Mar
2015
18 Mar
'15
11:07 a.m.
On 2015-03-18 16:28, Paul Koning wrote:
I'm not sure RSTS/E needs to explicitly know if there are Unibus memory,
except if you end of with non-contiguous memory because of this.
Johnny
So what happens if one does a reference to
something in the range 17 000 000
to 17 757 777 on the 11/84? The 11/84 _does_ support having memory on the
UNIBUS (up to 248KB), _but_ how it appears depends on how much there is. (See
section 3.13.2, EK-1184-TM-PR2.) There's a special register to configure it
(the 'KTJ11-B Memory Configuration Register', KMCR), which includes _how
much_ UNIBUS memory there is.
...
Basically, it seems like DEC was determined not to waste any address space on
the J-11/UNIBUS machines. Either it's configured as UNIBUS memory, or it's
PMI.
Interesting. I was referring to what I learned by reading the RSTS/E memory size
determination code. That code says that the main memory limit is 2M - 128kW for 11/44 and
11/70, and 2M - 4kW for J-11 Unibus. So it looks like RSTS/E doesn?t support the mixed
case you mentioned, only the ?just PMI? flavor.