Cool . Just make sure programs cannot be dependent on 128 KB of RAM pages, though, else those programs will have a limited audience, like the 85, 86 and 92 calculators, since the last calc to have 128 KB of RAM was in early 2007.

Nice

Nice!  * ZTrumpet hopes coding's going smoothly.

Update
Flash writing now works great!  You can change the value of anything in flash memory.  Still to-do are page erasures, and for some odd reason, the flash write routine doesn't return correctly, but that should be easy to fix.

Cool! Tested thoroughly and all?

I have a concern about compatibility with my 83+, though... as it doesn't support app compiling in Axe...

Cool! Tested thoroughly and all?

I have a concern about compatibility with my 83+, though... as it doesn't support app compiling in Axe...

Tested thoroughly, not really.  As for Axe stuff with apps, I'm not entirely sure how this applies...

As for scheduling, there is only 6 MHz to go around, 15 at best, so the scheduler is as fast as possible and simply moves between threads.  Each thread has the same priority, although I will eventually add implementation outside the kernel for moving threads out of the thread table if they are asleep.
Communication between threads, I was thinking of synchronized threads and shared-stack threads.  Synchronized threads are running right after each other with a shared stack, and several helper methods would be there to keep them in sync, such as SyncWithSister (input A=any number), which would pause execution until the other thread calls SyncWithSister (A=Sister's chosen number).
Shared stack threads share variables and stack, and merely run different code.
ExecProgram and StartThread return the thread ID in A.  SendToThread sends HL to thread A, and RecieveFromThread returns HL and the thread it came from.

A common syncing mechanism for commercial RTOSs is via something called a semaphore.

The APIs I see used most often are:

WaitForSemaphore(Semaphore* semaphore);
ReleaseSemaphore(Semaphore* semaphore);

and

SemWait(Semaphore* semaphore);
SemRelease(Semaphore* semaphore);

The task waiting on the semaphore is basically pended (or blocked/asleep) until another thread releases the semaphore. Hence, a great way to sync 2 tasks.

Anyway... just throwing some ideas at ya.