Long have we known that the TI-83 Plus calculator, and its predecessors like the TI-83 and TI-82, can be overclocked by replacing a single capacitor. Those calculators use what we electrical engineers call an RC tank, a circuit created from a resistor and a capacitor that oscillates. You can create an RC tank circuit that oscillates at f Hz by picking a resistor value R and capacitor value C such that f = 1/(2πRC). Unfortunately, RC tanks are quite sensitive to temperature and battery voltage, and tolerances (manufacturing variations) of resistors and capacitors mean that RC tanks in the real world don't produce precise frequencies. Therefore, for the TI-83 Plus Silver Edition and its children the TI-84 Plus, TI-84 Plus Silver Edition, and TI-84 Plus C Silver Edition, Texas Instruments logically switched to a crystal oscillator. Until very recently, we believed that the fixed speed of the oscillator meant that overclocking the later calculators was extremely difficult, if not impossible. However, one bricked calculator and one overclocked calculator later, with extensive photography and co-experimenting help from DrDnar, I have successfully overclocked a TI-83 Plus Silver Edition to run at 6.03 MHz, 15.95 MHz, 19.38 MHz, and 22.416 MHz.



The left screenshot shows the results from DrDnar's CPU speed test on an unmodified calculator, while the right screenshot shows the modified calculator. TI included four speed modes on calculators from the TI-83+SE on upward, but the top 3 speeds have always been approximately 15MHz. Over the past few days, we have experimented with unpopulated resistor locations on the TI-84 Plus-family PCBs, hoping that two unpopulated resistors might enable what we always assumed were planned 20MHz and 25MHz speeds when 0-ohm resistors were added. Although this proved fruitless, we made another breakthrough today when I discovered an interesting mapping of a set of four resistors on the TI-83 Plus Silver Edition mainboard, documented in a Cemetech topic. Much soldering and trial-and-error later, I was able to get the calculator running stably up to 22.4 MHz. Any faster and memory reads and LCD writes get unpredictable. Although ports $2E and $2F can be used to let the calculator safely run at speeds up to an estimated 28 MHz, the effective CPU speeds are actually lower due to the added delays.

As an added bonus, we believe this technique can be used to overclock even the TI-84 Plus C Silver Edition, a modification that I will attempt tomorrow. Combined with Calc84Maniac's discovery of an LCD feature that lets us double the rate at which we can transfer whole screens of data to 10FPS, this modification would allow programs to write the LCD at up to 15FPS. If DrDnar or myself succeed in overclocking the TI-84+CSE (which is now shipping from several distributors), we'll let you know.


My modified TI-83+SE. I added a 4-pin socket to let me easily swap out resistor values

Source:
http://www.cemetech.net/forum/viewtopic.php?t=8936

The Frogger link is wrong, and it was created by me, not Elfprince.

Great job, team! This news is also available on Cemetech, where I will be posting a full review of the calculator later today. I also plan to post news about the first graphical ASM program for the calculator to directly manipulate the LCD, as well as the hinted jsTIfied upgrades to support the TI-84+CSE.

You can now enjoy your TI graphing calculator right from your iOS6 Device! jsTIfied, Cemetech's online TI-83 Plus and TI-84 Plus emulator, is now a fully-functional emulator for Apple iPad, iPhone, and iPod Touch devices. The key breakthrough to make this a reality is the ability to encode a ROM in JPEG image data. You can use jsTIfied on a computer to export your ROM as JPEG file, which you can then send to your iOS device over iCloud, email, DropBox or iTunes. Once completed, you can navigate over to jsTIfied and upload the image as if it were a normal ROM. The steps required to download the image are on the jsTIfied page under the "ROM" tab. Remember that sharing of ROMs is illegal, even in this JPEG state.

Some drawbacks to using jsTIfied on your mobile device are speed and the lack of repeated button pressing. For speed, if your ROM fails to load it's best advised to close all of the apps that are running in the background. If you're still struggling for speed restart your device. The iPhone/iPod will run significantly slower than the iPad and in turn, the iPad significantly slower than the computer. When using the mouse in Doors CS, iOS will select the HTML box that contains the on-screen calculator and ask you if you'd like to copy it rather than continue that key press which will make navigating slightly more difficult as well as games that require you press and hold buttons, perhaps even pressing them rapidly. As such, jsTIfied on your mobile device is recommended for actual class related calculations!



Thanks goes out to Runer112 & comicIDIOT for testing the process on their devices and benryves for providing valuable JavaScript pointers. As always, if you have bug reports feel free to submit them!

Thanks also to comicIDIOT for his excellent original article on Cemetech.

What do you mean?

TI told me about 10 times that we weren't supposed to announce anything about this to anyone before 8am CT / 9am ET.

Do you mean it supports all of those calcs already now or is it the plan? I know the last time I tried it I could load 76.Fr, 82 Stats.Fr, 83, 83+ and 84+ ROMs, but couldn't get 73 to work and haven't tried 81 and 82 yet. Do you plan TI-85 and 86 support as well?

The news article I just posted on Cemetech answers all of that. Over the past few days I created a core for the TI-82 and skins for all the other calculators I listed. They all seems to work with every ROM I have dumped from my calculators. There's no TI-85/86 support planned at this point, although I may easily get bored one day and implement it.

Is Weregoose still around? Math genius.

Yup, he's a frequent Cemetech contributor. I've tapped him as one of the book's reviewers.