[Simh] Fixing the FP11's use of MMR1

[Johnny Billquist]

On 2018-11-14 02:58, Paul Koning wrote:
> 
> 
>> On Nov 13, 2018, at 3:45 PM, Ethan Dicks <ethan.dicks at gmail.com> wrote:
>>
>> On Tue, Mar 24, 2015 at 5:07 PM Bob Supnik <bob at supnik.org> wrote:
>>> This issue, pointed out by Johnny Billquist, has been hanging fire for
>>> years.
>>>
>>> Fixing the FP11's use of MMR1 - implementation proposal
>>>
>>> As has been noted, the FP11 does not update MMR1, ever....
>>
>> This was very interesting and educational to read, but when does it
>> matter?  Diagnostics?  Are there any live programs that depend on this
>> behavior?
> 
> Interesting question.  FWIW, RSTS does not use MMR1.  It saves it in crash dumps but never touches it anywhere else.

I haven't made a proper check in RSX, but at least I know that if you 
get a memory address error trap in RSX, the contents of the MMU 
registers are saved on the stack, and the user level program gets them, 
and then the user level program can do whatever it want with the 
information, so it is used in the sense that it is provided for 
applications to potentially make use of.

   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