The TI nSpire with the TI84 keypad (which emulates the 84 Silver Edition) is a more economical option for those needing an 84.

They can be had for under $20 on eBay with some searching. 84's are still commanding a far higher price.

-TRS80

Although that may be the case, the emulated calculator does not emulate undocumented opcodes, such as those that deal with IXH and IXL. This reduces the compatibility of programs that can run onvthe calculator, most requiring modifications to work.

If you want to transfer programs from your computer, you must have the same kind of cable that works with the TI-83 Plus, which is expensive. The reason why is because TI never bothered emulating the USB controller. More information can be found here.

I also own a TI-Nspire with a TI-84 Plus keypad, so feel free to ask any questions if you have any.

Thanks for the info. My post was aimed at say, a family with a high school student faced with buying an 84 because they need it for school.
The features you're describing would more fit one of us hobbyists rather than a student who needs one for school. They can get along without being able to install other programs, or link to a computer.
I had a work colleague who knows that I'm a calculator aficianado ask if I had an 84 he could borrow because he had sticker shock when he went to buy one.
I do have many calcs- but only one 84. I lent him an 84 nSpire and he reported back that it worked just fine for his kid.

Good thinking, trs80! I think a lot of students are not aware that you can make the oldest TI-Nspires be TI-84 Plus calculators, and it is indeed a cost-effective solution. In fact, I have 20 TI-84 Plus keypads sitting in a bag under my desk, and I really should put them on eBay for cheap at some point to help folks with this.

I still remember back when I saw Staples selling the TI-Nspire Clickpad with a 84+ keypad included for $10 less than an actual TI-84 Plus even though the emulated calculator is the Silver Edition with larger archive. I developed Illusiat 13 almost entirely on the TI-Nspire 84+ keypad and it worked pretty well and ran almost at the same speed as the original calc (that used to not be the case in older OS versions, though).

Does anyone know if the TI84 keypad is compatible with TI-nSpire CX and CX II CAS?

I can only see pictures with the original TI-nSpire.

Thanks!

No. Only with the non-CAS Clickpad and Touchpad models.