1 Mar
2018
1 Mar
'18
4:39 p.m.
On Thu, Mar 1, 2018 at 9:04 AM, Paul Koning via cctalk
<cctalk at classiccmp.org> wrote:
That's true when the MMU is disabled; if so it
supplies 1 bits for the upper bits for page 7,
and zeroes for the other pages. But if the MMU is enabled, all mapping goes through its
mapping
registers, and page 7 is no longer special. By software convention, kernel data page 7
is
configured to point to the I/O page, but that isn't required. If you wanted to be be
perverse you
could map the I/O page via page 6 and confuse a whole generation of programmers.
So if the I/O page is completely (all processor modes) unmapped is
there any way to recover besides a power cycle? Does the RESET
instruction disable the MMU?
-chuck