And yes, TI calculators have indeed been improving, apparently.
The TI-84 Plus is a graphing calculator made by Texas Instruments which was released in early 2004. There is no original TI-84, only the TI-84 Plus, the TI-84 Plus Silver Edition models, and the TI-84 Plus CE. The TI-84 Plus is an enhanced version of the TI-83 Plus. The key-by-key correspondence is relatively the same, but the TI-84 features improved hardware. The archive (ROM) is about 3 times as large, and the CPU is about 2.5 times as fast (over the TI-83 and TI-83 Plus)[citation needed]. A USB port and built-in clock functionality were also added. The USB port on the TI-84 Plus series is USB On-The-Go compliant, similar to the next generation TI-Nspire calculator, which supports connecting to USB based data collection devices and probes, and supports device to device transfers over USB rather than over the serial link port.
The TI-92 wasn’t allowed on standardized tests due to the qwerty keyboard layout making it be classified as a computer device in the US. The TI-89 has the same CAS functionality as a TI-92 Plus, but in a standardized test approved physical form factor.