The embedded world has been changing over the years.
20 years ago, one practically had to use a “PC” operating system to get a filing system, ethernet, etc. Today you can do it with FreeRTOS, FatFS, LWIP and countless other open source modules.
A lot of open source stuff is junk and a lot of it doesn’t even work but there is a lot out there, if you don’t mind spending months fixing bugs, and if you are a company which wants a software quality “audit trail” you can always find stuff which costs real money 
I would expect Garmin use a proprietary RTOS. Avidyne historically had fewer resources so I am not surprised they used NT Embedded. Is there anyone here who works in the aircraft or vehicle business? @neil?
Peter wrote:
20 years ago, one practically had to use a “PC” operating system to get a filing system, ethernet, etc. Today you can do it with FreeRTOS, FatFS, LWIP and countless other open source modules.A lot of open source stuff is junk and a lot of it doesn’t even work…
Even more than 20 years ago, you could get a RTOS with filesystems and networking that was open-source and definitely not junk. One such example is RTEMS, developed as a project of U.S. Army Missile Command, no less.
Sure; they were around since micros first arrived, but expensive. OK for a mainstream product though.
There is a particular RTOS which is used a lot in avionics; can’t recall its name.
Peter wrote:
There is a particular RTOS which is used a lot in avionics; can’t recall its name.
VxWorks? Lynx?
VxWorks.
VxWorks is the only RTOS to support C++17, Boost, Rust, Python, pandas, and more, as well as an edge-optimized, OCI-compliant container engine — enabling you to use the languages, tools, and technologies you love most to innovate where it matters most.
Got to be good – has an “engine”
VxWorks is ubiquitous, it’s even in some Wi-Fi routers, including consumer-grade ones.
Their runtime license must have shrunk from the $1000 in the old days
Does anyone know what is used in GA avionics?
Peter wrote:
Does anyone know what is used in GA avionics?
Peter, last I check (2 years ago, should a message on this forum) it was: VxWorks, LynxOS-178, Nucleus RTOS, INTEGRITY-178, SafeRTOS. For VxWorks I think it was Wind River.
If you google for RTOS and avionics you will find those…
Peter wrote:
VxWorks is the only RTOS to support C++17, Boost, Rust, Python, pandas, and more,
I though it is the language implementation that supports the OS and not the other way around? But what do I know, I’m only a computer scientist while the person who wrote the part that Peter quoted is probably a marketer of sorts.
I’ve been coding on top of FreeRTOS for a year or more and while you are right in principle, one still needs the right API for the language one is using.
For example FreeRTOS could not be used with, say, Pascal, because the whole thing is in C (I have never used C++ and never want to). One could do it by writing a translation layer, which moves the function parameters around; different languages tend to store function parameters in different registers, or differently on the stack.
The choice of development tools, operating systems, etc, is often made by management (read: at best, people who used to be programmers and when they reached the grand age of 40 they got sick of reading yet another 1000 page manual, so they moved into management) and not by the people who have to actually write the code That’s why you get BS websites like the Laravel one pushing the product to “web artisans” 
I would be surprised if Garmin used an in house written RTOS. I wrote one myself in the 1980s and a simple one is simple enough to do but it would be unusual.
