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Certain Texas Instruments graphing calculators (in particular, the TI-89 and TI-92 model series) use the Motorola 68000 processor, so these are called 68k calculators.

In chronological order, by year of introduction:

TI-92 (1995)
This calculator was Texas Instruments' first 68k-based calculator.
TI-92 II (1998?)
The TI-92 II is a rare model of calculator. You'd be very lucky to find one for sale anywhere.
TI-92 Plus (1998)
The TI-92 Plus was the first 68k calculator to have Flash memory (rewritable ROM).
TI-89 (1998-2004)
This is essentially a TI-92 Plus in a vertical form. The screen is smaller, with fewer pixels. The operating system is essentially the same.
Voyage 200 (2002-present)
The Voyage 200 is a newer horizontal-format calculator, about 2/3 the size of the TI-92 but with the same size screen.
TI-89 Titanium (2004-present)
This calculator is the descendent of the TI-89. It triples the amount of Flash memory, but doesn't add any more RAM. It has USB, unlike all other TI 68k calculators.