The TI-89 has a 160x100 LCD.
The TI-92 and TI-Voyage 200 have a 240x128 LCD.

But you can run TI-92 Plus assembly games on the TI-89 and their display won't be corrupt.
The only problem is that the display is cropped:

It means the all those calculators are sharing a 240x128 display buffer, which is partially displayed on the TI-89.



All those calculators accept a 240x128 TI-ViewScreen panel, usually used by teachers to show the display to the whole class.

In the case of a TI-89, only the top-left part of the panel is used with the OS:



In that case, what would happen if an assembly program wrote data in the screen buffer outside the 160x100 zone?
Success! Although the game display is cropped on the TI-89, the whole screen buffer is displayed on the external panel.



But of course, this was a VSC version of the TI-89 with the additionnal proprietary  ViewScreen connector.
The panel can be plugged on every TI-89 Titanium using an adaptator for the mini-USB connector: the TI-89 Titanium Presentation Link.

So using this adapter, can this extended display been achieved on all TI-89 Titanium calculators?
Success, again!



So it's quite interesting!
If someone has the time, it means we could develop an external 240x128 display for the TI-89 which would be plugged through the mini-USB port, the 1st step into performing some kind of an "upgrade" of the TI-89 into a TI-92 Plus / TI-Voyage 200.



Credits for the idea of the experience go to Lionel Debroux.



Source with more information and images:
http://tiplanet.org/forum/viewtopic.php?t=9511&p=125807

That is pretty nice

Well these viewscreen are rare for students

That's pretty cool. If you were writing just TI-89(t) programs, you could probably use the extra space for debugging info or something, or hidden messages. That sort of reminds me of once when I was fooling around in Command Post Plus and poking in random bytes like my name in the off-screen area of the 89 LCD buffer. If you don't reset the calc or run ASM programs that use the full buffer, it can invisibly remain there for quite some time.

It would be cool if someone found a way to make an inexpensive external display. Or even a large, bright LED display, hehe.

Quote from: aeTIos on June 21, 2012, 12:14:14 pm

Would this also be possible for the 84+?

No, because the 84+'s buffer is only 94x64.

Actually, it's 120x64. I'm sure that a program that reads LCD commands from the USB would be able to display that whole area.

^that Really cool stuff O.o

Well, indeed I would be positively surprised if this happens.
How long would it take for the USB port to send 1024 bytes of data?

Quote from: blue_bear_94 on June 21, 2012, 12:27:04 pm

Quote from: aeTIos on June 21, 2012, 12:14:14 pm

Would this also be possible for the 84+?

No, because the 84+'s buffer is only 94x64.

Actually, it's 120x64. I'm sure that a program that reads LCD commands from the USB would be able to display that whole area.

Actually, it depends on the calculator. Mine, as I've determined from several tests, is 96x64. The most important result is that, when the LCD is in Y-autoincrement mode, after the 12th/16th column (8-/6-bit mode, respectively) it wraps back to the first column, not an invisible one offscreen. Mine's also the one with the extra commands to flip the display, which gives me the impression it's a different driver.