I've had a TI-84+SE for a few years now, and it's served me well throughout high school and through most of first-year engineering. There are things I really like about it:
- Really efficient, simple interface
- Great keyboard layout with nice big buttons
- MathPrint is really essential to me
etc.

I rarely graph with it, but use the functions, tables, solver etc. regularly. I also regularly use it linear algebra tasks like systems of equations.

I have friends with a CXII CAS, and the CAS clearly opens up so many possibilities, with things like
- Symbolic Calulus
- Symbolic Matrices
etc. I have a feeling I would learn lots of other useful tricks with CAS if I had one.

So if I wanted to upgrade to something with CAS, what would you recommend? The CXII CAS is very expensive (even on used market), and in my time using nSpire models (my HS had a class set), the tiny keys and touchpad are inefficient to use. I'm sure it wouldn't be as bad if I got used to them, but how much? Also, how much difference is there between the different nSpire CAS models, especially if I'm not graphing? The original one from 2007 seems interesting with the bigger keys and no touchpad, but I'd like to hear from someone who's actually used it. Older models like the 89 have no MathPrint, right? Do they bring anything interesting to the table?

I know there's a lot of questions here, but I figure you all probably know the calculators well enough to give great advice.

Thanks,
Ron

Several notes:
* 2D expression pretty-printing has been a standard feature of TI's CAS-equipped calculators since the TI-92 in the mid-90s. The Nspire series has inherited it from the TI-68k series.
* many of the keys on the Clickpad Nspire keyboards are even smaller than those from newer Touchpad, CX & CX II models, so you wouldn't like them either, I'm afraid
* the CX II CAS is the only CAS model still maintained by TI.
* you can get a good CAS on a CX I (even non-CAS) through KhiCAS, but this requires using a slightly older version of the OS, one supported by Ndless. If the calculator has already been upgraded to a newer version, no luck at the time of this writing, due to the anti-downgrade protection and the lack of an arbitrary code execution vulnerability (which would make it possible to erase the anti-downgrade protection information) on the newest versions.

Thank you! Those are very helpful notes.

Based on what you said about the 68k models, I figured I would borrow an 89 Titanium from a friend and try using that for a while. I knew it has a good CAS and supported unit calculations, but there were some other features I really liked, particularly the Custom Menus and kbdprgms. Seems like it could be super efficient with some practice. Still, while it does pretty-print your entries when they're submitted, it's really hard to deal with not being able to see them in the entry bar. There isn't really any way around that, is there? The other unfortunate thing is the screen. The small pixels make viewing angles way more of a problem than on an 84, and poor light conditions can lead to a lot of eyestrain, or neck strain trying to hunch over it. Still, there's a lot to like about it, and it can be had for way cheaper than the nSpires.

here's my two more questions:
how do the screens on the old non-color nSpire models compare to the 89 Titanium? Better or about the same?
Second, (and much more subjective): Do you feel like the nSpire models are much more cumbersome than the 84/89/92, or do I just need to get used to the way they work? Does clickpad vs. touchpad have much of an impact on this?

Again, thanks so much for the help.

Yes, borrowing a 89T from a friend to use it for a while is a good idea. There are two other virtual calculator options for testing the calculator's software itself, but you'll miss the look and feel of the physical calculator, obviously:
* TIEmu and the AMS 3.10 OS upgrade downloaded from TI's website;
* https://tiplanet.org/pad_ti68k_emu/ & https://tiplanet.org/emu68k_fork/ (nicer UI) and the same OS upgrade.
The emulator engine used by the latter only requires a Web browser, but these Web-based emulators aren't really designed for ongoing use: TIEmu's savestate functionality is much better suited to that use case.

There is a 2D pretty-printing equation writer for the TI-68k series, Samuel Stearley's EQW/Hail: https://web.archive.org/web/20040404064828/http://www.calvin.edu/~sstear70/exw.html .

The screens for monochrome Nspires are terrible, slower and more blurry than the TI-68k series' screens.

I'm much more used to the TI-68k series than to the Nspire series, so I'm biased, but the small keys on the Nspire series, be it on Clickpad-type keyboard or on Touchpad-type keyboard, aren't quite universally considered easier to use than combos of alpha + larger keys provided on the TI-Z80, TI-eZ80 and TI-68k series, especially by people who have used these models for years

If you're going to try a 89T, I would highly suggest you find a way to try an Nspire CX II CAS as well... you should see the decades difference by yourself

There is the Equation Writer app that lets you edit and execute equations in pretty print. I find it cumbersome and tend not to use it, but then I also don't care much about pretty printing anyway.


I only have an 89T and an Nspire CX I CAS, so I can't compare to the greyscale Nspires, but I heard they're worse than the 83+. My 89T on the other hand is definitely better than my 84+, in terms of contrast and pixel response time. The greyscale in games is also so much more flickerless. The viewing angle is kind of annoying but in my opinion only becomes an issue in a few games, not very much in general math use.


Like I said, I have both an 89T and an Nspire CX I CAS, and I basically only ever use the 89T for actual math. The Nspire can kind of do more and is quite a lot faster, but the worse keypad, slower OS, more cumbersome Document system, and lack of customisation made me lose interest.

More on all of those:

• The Nspire's keypad keys are harder to press, more clicky, have sharper corners, and I often end up with sore fingers after some use. They're also really annoying with long nails which you probably don't care about but I do. Also, the CX's touchpad is a gimmick that mostly makes navigation more cumbersome and I ended up using the keyboard shortcuts mostly (which aren't documented anywhere!). I'm pretty sure the old clickpad keypads are alright, but they still do have very tiny keys.
  
• The time between me pressing a key and it appearing on the screen is very noticeable. I would say .2s or so. Some people don't mind or don't even notice, but I do. Overclocking made it slightly better, and the CX II could be great. I don't know.
  
• Why does everything need to be stored in a Document? The scratchpad has such limited functionality. Programs need to be stored in Documents too and aren't accessible outside of it.
  
• The 89T has excellent native code execution, hook support, TSRs, all the file formats are pretty documented and otherwise not hard to figure out (while the Nspire's tns files are actually encrypted). And not to mention that the OS and Apps keys have been factored and you can just apply patches to the OS itself.
  

Oh. Probably useful information: my Nspire CX (HW revision AB, manufactured in 2016) I won at a mathematics competition and upgraded to CAS a few years later (which you can AFAIK still do on the newest CX I models and no one has mentioned). My 89T I got second-hand for €40. It's a rev K from 2011.

You gave quite a few arguments that are based on your experienceand may not reflect some things that would be high on the list of someone who would use the calc mostly for math (hooks, TSRs... even though all this exists just fine with Ndless, but anyway...), so let's try to focus on that topic, I guess. (That said, if programming is an important ask, at least the Nspire can natively do Lua and Python in addition to Basic)

The Nspire is indeed more complex in its architecture, you'll "have to" think of it (when authoring documents anyway, for usage, it doesn't actually matter much) as a mini computer, with folders and files and applications interacting with each other.


They've always been documented though.


Yeah overclocking is nice on the pre-CX II, but on those it's not actually needed.


Honestly, nowadays it's not that hard to find a 89T for <= $20 and a Nspire CX CAS for $50, and CX II CAS for <= $70.

In addition to my own calculators, I have a few Nspires on loan from Adriweb and mr womp womp. I've spent a fair deal of time with a first-generation Nspire CAS, a Nspire Touchpad, and a Nspire CX CAS over the last year, and I've used the TI-89 Titanium, TI-92, and Voyage 200 for many years. I've settled into using the Nspire Touchpad for about 90% of my use cases, and a TI-73 Explorer or TI-92 when I need to run a program to obtain a result or when I need to perform on-site math quickly (although the Nspire's Scratchpad makes on-site math possible, it's a bulky calculator compared to the TI-73 Explorer). I'll explain why I stopped using 68k, and why you probably shouldn't start if you have to choose between 68k and Nspire.

The rechargeable battery feature added to the Nspires with the Touchpad models is an absolute necessity given the poor battery life of these calculators (the grayscale Touchpads support dual AAA/Li-ion power as well). Battery life on the original Nspire CAS is about a month in every-other-day usage, since big screen and big CPU need big power. Grayscale Nspires with a rechargeable battery get just as much battery life out of the rechargeable battery compared to AAA batteries, and you can just plug the calculator into a phone charger or computer for a few hours and it'll be good for another month. Touchpad calculators need the TI Rechargeable Battery with Wire, which is the same battery used on the TI-84 Plus C Silver Edition and earlier Nspire CX models; TI still sells this directly on the Education Technology Store.

You can't have CAS, Li-ion, and Clickpad on the same calculator*, but there's no point in having that combination: the Clickpad keypad is an absolute nightmare. The little nubby alphabetic keys are raised quite high over the rest of the keypad, and you'll spend far more time trying to correctly enter information or correct inevitable typos than you will doing anything else on those early Nspires; it gets in the way of being able to enjoy the rest of the Nspire OS and it causes the product line undeserved hate. I cannot empahsize enough how much of an improvement the Touchpads are. Touchpad has its own limitations (I'll get to those later); I just want to be clear that there is no reason to even consider a Clickpad. Early Nspire CASes run cheap for a good reason.

People like to complain about the screens on the grayscale Nspires. These complaints seem to come from people who don't know what a miserable screen is actually like. TI has given us much worse on the TI-83 Plus and TI-83 Plus Silver Edition. Alternatively, go with a CX model and work in the dark!

Math is so much better on the Nspires. Equation entry on the Nspires is a breeze, especially larger equations. Forget a parenthesis? Type the closing parenthesis and the opening parenthesis gets added in. Quality of life improvements like that on top of WYSIWYG prettyprint editing both make it easier to do complicated math and figure out if/where there was a problem in the equation entry. 68k will only prettyprint on scrollback, so stacking division or nesting functions can make a mess. Nspires also have an initially-confusing document structure to parallel the Student Software, but it allows for tremendous flexibility when switching between problems or workspaces.

The graphing on Nspires is significantly faster than on 68k (probably by an order of magnitude or so), especially when you're comparing against a large display 68k like a TI-92 Plus. It's another quality of life improvement.

I haven't explored programming on Nspire very much, but all I know is that 68k TI-BASIC is far more powerful. On OS 3.9, Nspire TI-BASIC is more of a series of automated homescreen commands than anything and basic functionality you're expecting out of a programming language, particularly around I/O, is lacking or absent entirely. Later Nspire OSes have made improvements, such as making I/O possible to a degree, but the implementation is fundamentally flawed.

While the Touchpad makes improvements over the Clickpad, it still has a learning curve. Many common functions you'd normally find directly on the keypad, like the trig functions, aren't exposed directly; you press the key to open a menu of functions à la TI-73 Explorer. You still retain the option of typing in the function name directly. The alphabetic keypad on the bottom of the Touchpad is not mushy rubber mat like TI-83 Plus buttons or the rest of the Touchpad keypad, but rather it has a responsive click and is easier to type on than it looks. If stubby fingers are an issue, than the Clickpad is impossible to type on without hitting neighboring keys. As far as the menu system goes, you really do get used to it. It's still faster than navigating a Clickpad.

Nspires are tied into the Student Software quite a bit. Unlike on other TI calculators, Nspire files transferred to a computer can't be opened in a program analogous to TI-Connect; instead, they need the paid TI-Nspire CX Student Software in order to be opened. Pretty much all of the Nspire's functionality is present in that program, but you also have the option to take advantage of the computer's larger screen. It sounds like something you might want, but it's subscription-based software around $30/year. There's a 30-day trial if you want to mess around with it.

If the calculator's going to be used solely for math, I'd recommend some kind of non-Clickpad Nspire device. It doesn't really matter which if cost is your main concern, but get the rechargeable battery (with wire) if you get a grayscale Nspire that doesn't come with a working one. I feel that the grayscale models are a bit more responsive than the original CX model, but if you can afford any CX then just go for one; the interface is the same, but in color on a lighter/smaller device with some OS improvements.

If you want to write programs on-calculator and use the CAS (which I get the feeling you don't), get a 68k. If it's legal for whatever educational purposes you have, try for a TI-92 Plus or a Voyage 200. Those should be in the $40 ballpark. Otherwise, shoot for a TI-89 Titanium.


*We get it. Shut up.

Let's note that on the CX II series, programming got way more powerful, not only because TI-Basic got a big amount of new features (mostly for IO and graphical programming), but also beacuse Python was added.
Before that (on the CX), only Nspire-Lua was able to do all that (and still is, and faster than Basic or Python)

Wow, thanks everyone for all the replies and information! There's definitely a lot to consider, and I'm not surprised that there might be a little contention between supporters of the 68k and the nSpires.

First, thank you so much for pointing out those equation writer softwares! I tried both, but I think I prefer the one fghsgh linked: I like how it keeps the default shortcut menu and allows using the same custom menu I made for use on the home screen. It feels much more integrated, and totally changes the way I use the device, although the tree-based entry system certainly has a learning curve. It's also cool how it has an API. I wrote a hotkey program that allows scrolling through the previous results on the home screen to paste one in, similar to how that's done on the entry line or on a TI-84. I'm surprised it doesn't include anything like that - it didn't take too long to write and makes the type of multi-part calculations I would do in a Chem or Physics class much more efficient since I never even need to leave the equation writer to reference previous answers.

The clickpad nSpires definitely seem best avoided, between the screen, keypad and battery it sounds like I want nothing to do with them. And as for the monochrome touchpad one, I wouldn't want to take a chance on a screen any harder to read than the 89T, although I'm getting conflicting messages on whether that's actually the case.

I had no idea you could just upgrade a CX I non CAS into the CAS version. I see people selling the non-CAS CX for pretty cheap, so sounds like a decent deal.

At this point I feel like the 89T is a pretty solid device without any massive flaws, though perhaps I might find an nSpire more appealing if I got used to it. I probably won't have a chance to borrow one since my friends who have them all use them regularly, but maybe that's saying something.

I suppose I'll keep borrowing the 89T for now and kick that decision down the road, since it doesn't seem at all clear-cut. But I feel like I can make a WAY more informed decision now when the time comes.
So again, thank you all.