Hi, please note that some PPC derivatives (especially those for embedded projects) usually have eight DBATs and eight IBATs. This feature must be enabled (e.g. in a 603e core) with a special bit in one of the HID registers, but it will put the number of BAT ranges closer to what is needed in embedded computing.
The advantage of BATs versus pages is definitively, that they usually get set up ONCE during startup and, due to their flexible size, will not need to be reloaded. Note that the pages usually only cover 4K of memory, and the "translation lookaside buffer" (TLB) only maintains the last 16-64 used pages, so there is always code involed reloading the required page info into the TLB. IMHO this reduces the realtime performance of the system. In short: Supporting both (BATs and pages) in libmm would be a good feature. wkr, Thomas. On 22.06.2013 04:11, Chris Johns wrote: > Hesham Moustafa wrote: >> Eight: 4 for data and 4 for instructions. BAT areas can not overlap. > > Then I suggest we support for pages as well. There may be a need for > more areas in the future and I feel 4 may not be enough. > > Chris > _______________________________________________ > rtems-devel mailing list > rtems-devel@rtems.org > http://www.rtems.org/mailman/listinfo/rtems-devel -- -------------------------------------------- Embedded Brains GmbH Thomas Doerfler Dornierstr. 4 D-82178 Puchheim Germany email: thomas.doerf...@embedded-brains.de Phone: +49-89-18 94 741-12 Fax: +49-89-18 94 741-09 _______________________________________________ rtems-devel mailing list rtems-devel@rtems.org http://www.rtems.org/mailman/listinfo/rtems-devel
