TI-84 emulator. Need confirmation from real hardware

[Mario F.]

I've been working on a TI-84 emulator of my own for a few months now. Normally I can detect a bug on my end of the code (engine or UI). But this one is eluding me and I'm starting to suspect it's a TI bug, not mine.

I'm running a TI-84SE rom. I need your help confirming if this is the (wrong) result you get in your calculator. Unfortunately I can't do this anymore. One of the reasons I've been putting this project on hold. The original from where I extracted this rom was stolen from me 6 months ago while staying in a hotel.

[Matticus]

/*
    TI-30XIIS     = 25.36040482
    TI-85         = 25.3604048207
    TI-89         = 25.36040
    TI Voyage 200 = 25.3604
*/

[Mario F.]

Ugh! That can't be either. It should be a little larger than 11. What is going on? Are you adding them all?

[Matticus]

Oops, yes. Hold on a bit.

[Matticus]

/*
    TI-30XIIS     = 11.94399696
    TI-85         = 11.9439969557
    TI-89         = 11.94400
    TI Voyage 200 = 11.944
*/

[Mario F.]

Wow, LOL! Nevermind. Your mistake helped me find the problem. If you look carefully at the screen that's not a subtraction sign. That's a minus sign! So the emulator is doing what it is being asked, sqrt(101) + sqrt(74) * -3 * sqrt(5).

Another bug affected my key mappings and I was inserting a minus sign when hitting the minus key on the numeric keypad.

[Matticus]

Good find! I was wondering how the result became negative, but was too busy juggling the calculators to give it much thought.

[Epy]

The minus sign in your equation is the unary minus, not the subtraction minus, you're calculating:

octave-3.6.2.exe:1> sqrt(101) + sqrt(74) * -3*sqrt(5)
ans = -47.656
octave-3.6.2.exe:2>

Edit: too late, nevermind!

[Mario F.]

Hehe. Thanks anyways Epy. You would have nailed it.

[Epy]

Thanks, cool project by the way. I've been a big fan of calculator programming since high school. I'm afraid I'm on the HP side of the HP vs. TI battle though, I love my HP 50g and RPN mode.

[Mario F.]

I got so accustomed to the TIs, it's hard to see me going elsewhere. But my interest in emulating the TI 84 series has nothing to do with it though. It's just a continuation of my love for Z80 emulation and programming. I really need to stop doing this though and get some basic knowledge on electronics somehow. For a very long time I've been getting the itch for proper Z80 programming on my own custom made Z80 devices.

I did check the HP 50g on the web. Seems a much superior model to the TI 84 SE. But that wouldn't surprise me. The key combos seem also much richer (the TI lacks, for instance, n roots) and useful (the TI hides too much stuff under on-screen menus). But I have been dating the new TI Nspire series for some time.... tough decision.