Have you seen Fuzix? It's essentially exactly this: a V7-ish Unix ported to run on very, very small machines. It'll run happily on a variety of Z80, 6809, 68000, 8086 architectures etc. On a Z80 with a basic MMU, like my NC200 laptop, you get about 55kB of userspace per process, which is enough to run some compilers.
https://github.com/EtchedPixels/FUZIX In single-tasking mode it'll run on really absurdly small devices: I had it running, happily, on an MSP430 development board with 66kB of RAM, with a 25kB userspace (after severe hacking; it's since bitrotted). http://cowlark.com/2015-10-27-fuzix/ It makes ELKS look big. On Tue, 31 Jul 2018 at 19:40 Paul Osmialowski <[email protected]> wrote: > > Note this message came out of subj: ELKS Git repository up on > SourceForge + patches applied > > > Hello All, > > > JB>Additionally, I wish to continue discussing options for making ELKS > less 8086-specific, and moving to a compiler that can make ELKS more > easily portable. > > > The last discussion about ELKS possible way of porting/evolution was > going on here many years ago. As I remember, I've made short conclusion > for myself out of all those quite intensive message "ping pong" and > brainstorming. The conclusion was similar to: "The 8088/86/286 memory > access models make programming for those processors very similar to many > 8-bit chips and PDP-11. The 64kb limit is very strong and serious barrier > that is not possible to overcome without serious performance penalties > (e.g. FORTH or an virtual 32bit RISC CPU). The whole industry already > found the way out by switching to a new hardware with 24/32/64bit address > space, so most sources around the world is not possible to compile using > 64kb code/data segments. If you ever run any virtual machine on 88/86/286 > CPU with direct memory access to few MB of RAM then you would run ucLinux > instead of ELKS. So, the only possible way for the ELKS evolution is to > support EXE (i.e. multi segments executable) and probably support other > systems with 16bit address space limit (including those 8-bit and > PDP-11)." > > > Thanks, > > > Andrey > > ELKS on 8-bit machines? How cool idea is that?! This reminds me a good > hardware candidate for it, Zilog's eZ80 microcontroller with 24-bit > address space, e.g. eZ80F920120MOD board has 512kB extenal RAM which > should be enough for ELKS. Some time ago I managed to boot Nuttx on it and > telnet into it over TCP/IP (and Nuttx can run on various non-MMU > architectures too starting from 8-bit Z80 through 8086/8088 machines as > well as 32-bit ARMv7m MCUs e.g. Cortex-M4). In theory, old Z80-based MSX > machines were also well stuffed for their times (enough for ELKS), and > non-free modern-era OS'es like SYMBOS can prove good old Z80 is capable to > run multi-tasking OS (well, actually Nuttx also proved that). > -- > To unsubscribe from this list: send the line "unsubscribe linux-8086" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html >
