This is really impressive. I'm a bit confused, though: If it's based on descent, why are the screenshots focused on walking around? The Descent I remember had zero-G flying everywhere!

In any case, great job on the engine. It might actually give me a reason to use my recently acquired TI-89.

I've had this project sitting in a folder for over a year now, and I decided to pick it back up. I'm posting now because I'm actually making progress that I would consider release-worthy, rather than just a toy.

Everyone knows TI-OS is horribly bloated and slow, but we've built so much software into the existing system that no one's too anxious to leave. So, why not fix the problems and keep the OS as it is?

That's what I'm doing. Reprogramming bits and pieces of TI-OS to be faster, better, smarter, stronger, etc.

All the work is being done based on OS 2.41 for 84+SE at the moment. (Although, currently it's all taking place in page 00, so that's pretty much moot) Some of the optimizations will definitely be ported to the other models, but others (like improved USB) obviously wouldn't apply. Ideally, though, the modifications would converge to a single OS version that works on ALL the models in the 83+/84+SE range. (No, I'm not planning to support the CSE or CE. At least, not for now.)

If I release anything, to avoid copyright concerns, it will be patches against the ROMs I specify. It's a historically non-grey method of distributing hacked and modded software, so I hope I can avoid any nasty legal letters with this.

So, without further ado, here's what I've done so far: (I will edit this list with updates)

* Optimized LCD_Delay routine in Page00. It saves a minimum of 260 cycles per screen command on all models, for any software that uses the built in routines. (Not Axe, or most Asm). This results in roughly a 10% improvement in display-heavy routines in TI-BASIC, for example.

Here's what else I want to look into, but haven't done yet:

* The TI-BASIC interpreter (I bet this is loaded with goodies)
* Floating point optimizations
* Various frequently used system bcalls
* Improved Graphing (mostly through optimized fp and draw commands, but also ideally by not updating the screen until it's drawn fully)

Let me know of any suggestions, ideas, discouragements, etc. you may have.

LLVM is not particularly suited for z80. It assumes, among other things, the ability to do fast, stack-offset memory access. The z80 doesn't do that. The purpose for those accesses is to allow functions to exist once in code for arbitrary, stack-based memory locations.

SDCC on the other hand is designed with embedded CPUs like the z80 in mind. It uses a lot of RAM compared to assembly, and it's a fair amount slower, but still far above what LLVM would be able to produce without some miraculous IR conversions.

I'm glad to hear all that progress! Sounds like the ball's really rolling, especially with the C support. Maybe we could just port xcas and have working calculation software.

One question: Does the C compiler have a way to do text-based programs with the standard scanf/printf functions?

while(1):
 if(time()<0600): sleep(0400);
 for task in todo:
  if task.due < time(): panic()
  elif task.due - time() < 200: panicdo(task)
  else: sleep(0200)


I don't see how this would resolve the issue, since teachers wouldn't know if you had a way to revert it to the old mode. (Which, by the way, you easily could, using the standard OS-changing method)

Short answer: there's no way to do it permanently, or in any way that enforces the inability to do non-CAS functions given a few minutes.

You mentioned the ability to install a CAS OS on the non-CAS nspire. That method also works just fine in reverse. However, it runs from the calculator's RAM rather than truly installing itself. A simple reboot would get you back into the CAS OS, taking around 15 seconds.

If your primary motive is to save money, you could consider buying a used calculator. You can find used ti-83+ calcs on amazon for around $35.

Congrats on the Community Project subforum! It looks like you're making decent progress on this. I especially like the ability to write characters in multiple languages.

DJ zStart has a built-in font editor. You could put it in by hand with that, then save the var it creates.

Or, you could hex-edit an existing font. It's not compressed.