From: Andrei Chichak (acpmiedm_at_telusplanet.net)
Date: Tue Oct 07 2003 - 10:39:27 PDT
At 02:42 AM 10/7/2003 +0200, you wrote:
>a technical question: is the newton memory "protected"? from what i
>understood reading the FAQ, the answer is both yes and no...
It depends on what you mean by protected. There is the inter-process
virtual memory protection schemes of operating systems typically handled by
memory management units (MMUs), there is the use of batteries or supercaps
to protect static ram from loosing it's state, there is EEPROM or Flash ROM
to store data protected from loss of battery or supercap charge.
The ARM chips in the Newton do have MMUs and they are used in the Newton OS
for something like demand paged virtual memory where objects are pulled
from the object store. The object store implements a flash file system with
lots of compression so that objects are stored small and safe. For more
information on this stuff look at http://wsmith.best.vwh.net/works.html
The object system allows finding pointers to other objects in the system
(like other programs) de-referencing them and allowing you do munge the
results. This is used in the various soup debugging programs.
The memory space does not use protection between processes.
You can also place your version of system routines into the object lookup
hierarchy and mask system routines in ROM. So the operating system is not
protected from you either. This is how patches are able to override stuff
in ROM.
Andrei
> roman pixell
-- This is the NewtonTalk list - http://www.newtontalk.net/ for all inquiries List FAQ/Etiquette/Terms: http://www.newtontalk.net/faq.html Official Newton FAQ: http://www.chuma.org/newton/faq/
This archive was generated by hypermail 2.1.5 : Tue Oct 07 2003 - 11:00:01 PDT