> On Jul 9, 2021, at 11:40 AM, Joel Sherrill <j...@rtems.org> wrote: > > On Thu, Jul 8, 2021 at 3:11 AM Shiro <rt9f.3...@gmail.com> wrote: >> >> Hello, >> >> I’m new to RTEMS but very much like its features. I’m wonder what HW >> (MCU/MPU and memory size) RTEMS is typical used on. Anyone care to share a >> bit of details? >> > > Well I held back hoping more people on the using side would answer. > This is my perspective from the long-term developer view. > > Most users are on 32-bit platforms. There have been 64-bit ports for a > long time but most people aren't using them. > > There are a lot of users from the space community who tend to be on > hardened hardware. This SPARC LEON family is probably the most > commonly used there. In the early days of the LEON predecessor > (ERC32), I would say 1-4 MB was quite common for RAM. Other CPU > architectures have been used in RTEMS space-based systems like > PowerPC, Coldfire, MIPS, and ARM. > > There are also a lot of users in the EPICS (Experimental Physics and > Industrial Control System) community which is commonly used in high > energy physics, astronomy, and other big science equipment. I would > tend to put a lot of those users on VME and CompactPCI boards with the > PowerPC and x86 being common. They may still use some of their old > VME m68040 boards or at least we haven't dropped support for them. > These mostly tend to have 4-16 MB RAM. > > There are also a lot of commercial users and currently I think a lot > of those are on ARM platforms (STM, Xilinx, NXP, etc) with RISC-V > coming on strong. There are users on other architectures but I think > the bulk are there now. PowerPC users seem to be realizing they are on > the tail end of the lifecycle and need to look forward to a > transition. > > RTEMS has been ported to 16-bit CPUs but there are none currently in the tree. > > You can certainly have an RTEMS application which fits into a small > amount of Flash but as you add capabilities, you tend to pick up code > and data space requirements. The earliest RTEMS systems would be big > if they had 1-4 MB total Flash and RAM but that's considered small > these days in general. I recall one m68k based system that has 96K > total code and data space. The legacy network stack could easily run > on 1 MB RAM. Now libbsd generally has more features and takes more > memory. It may be able to be trimmed down but no one has invested the > time. lwIP would be a better alternative in those cases. > > If you need a lot of features, the footprint naturally grows. If you > are on a small target board, some tests won't fit. For example, some > of the file system tests assume a 1MB RAM disk. If you don't have the > space, you just don't. > > I still think that a large RTEMS system is on the smallest end of > Linux systems. > > Not sure this gives specific answers but that's my impression. > > —joel
Wow, what an awesome reply. Thank you for the detailed response, I appreciate your time. This helps me quite a bit. My take away is that RTEMS is not going to be a comfortable fit for Cortex M3/M4 MCUs with 64k to 256k RAM (although it can be shoehorned in with some work). This helps me partition the MCU/MPU space by RTOS. Thanks again, Shiro _______________________________________________ devel mailing list devel@rtems.org http://lists.rtems.org/mailman/listinfo/devel
