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My biggest gripe with the TI-83+ is its slow performance — it becomes painful when using this graphing calculator to actually graph stuff. There are many web sites that cover how to overclock this calculator, but unfortunately they all detail the procedure for revision F of the PCB. I have a calculator from around 2000 or 2001, and it's PCB revision A. I did some poking around near the main IC, and managed to figure it out.

Here's a short clip showing the end result. First, three sine waves are graphed at the stock clock rate. Then I flip a switch, and graph the same sine waves again, but at nearly double the speed.

An RC oscillator is used for the clock, so if you just reduce the capacitance you can speed up the clock. You can either replace the capacitor, or better yet, wire a second capacitor in series. By wiring a second capacitor in series you can use a switch to short out the new capacitor and return the clock to its original speed. This is helpful for two reasons: overclocking drains the batteries quicker, and playing games can get difficult when they run at almost double speed. The TI-83+ case doesn't leave much room, but there is just enough space for a small switch to be added in the battery compartment.

I probed all of the passives near the main IC, looking for any waveforms with a relatively high frequency. After a couple minutes I found the right capacitor and began wiring various capacitors in series. My particular calculator runs stable at up to about 10.2MHz. I can push it further, but the LCD starts to glitch. Pixels that should be black are not, and others that should be white are actually black. At about 13.5MHz my calculator's LCD would no longer work at all. Here's a list of the caps I tried in series with the stock cap, and the resulting clock rates I measured:

Stock clock = 5.5MHz
82pF resulted in 6.8MHz (stable)
27pF resulted in 8.7MHz (stable)
12pF resulted in 9.4MHz (stable)
10pF resulted in 10.2MHz (stable)
7pF resulted in 11.3MHz (LCD glitches)
4pF resulted in 13.5MHz (LCD will not work)

The clock rate is measured by probing the right side of the resistor located directly above the capacitor that is standing on end.

Here's the waveforms, stock and overclocked:

I hope this helps someone else with an old revision of the TI-83+.