Login [Register]
Don't have an account? Register now to chat, post, use our tools, and much more.
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
On my TI-84+SE (which has the same TA3 ASIC as the TI-84+CSE), I used wire glue to connect the terminals of two resistors, which on the TI-84+CSE are labeled R08D and R07D. This successfully boosted the CPU speed of the 6 MHz mode to 16 MHz, and the 15 MHz modes to 18 MHz. Unfortunately, the OS couldn't properly set the LCD write pointer sometimes (resulting in screen issues), so I decided to remove the modification and forgot to take pictures.
Very exciting! It's never any fun when you have to resort to a hardware mod to enable a feature that's limited by other hardware though. Do you guys see this gaining popularity for people to build - and most importantly play - games around it?

Or is this more of a "it's possible but there's no real world reason why we should embrace it" discovery?
Unfortunately, this is not a discovery that regular users can take advantage of, except on the out-of-production TI-83+SE. The pins on the TI-84+/C/SE aren't connected to unpopulated solder pads like on the TI-83+SE, so users would have to do some very hard SMD soldering directly to the ASIC.
And even on the TI-83+SE, if you're less clumsy than me and don't rip off a solder pad while you're experimenting (requiring you to solder straight to an ASIC leg anyway), the pads are quite tiny. That's 30-gauge wire in the photo, even though it looks like 24-gauge. As DrDnar says, this isn't going to be a popular mod except with people who already have some experience with fine-pitched soldering. One of the nice things about it versus 83/83+ overclocking is that because the speed is already controlled in software, there's no need for a physical switch to control the clock speed.
*bump* So, I spent some time trying to overclock my TI-84+CSE today, and I need to put a big bold warning here. The TI-84 Plus C Silver Edition's ASIC has microscopic pins! Even if you're a skilled EE with years of soldering experience, unless you have specialized precision soldering instruments and a microscope (yes, an actual microscope), don't even bother trying to overclock the TI-84 Plus C Silver Edition. Even if you try, you'll probably be unsuccessful. Evidence indicates it cannot be overclocked. Whew, that was bold. Anyway, since I was successful in overclocking the TI-83+SE yesterday, I took a crack at the TI-84 Plus C Silver Edition today. I cannot impress on you how tiny the pins are. I tried to tack down 30-AWG wires to the second and third pins in the lower-right of the ASIC, but after an hour of frustration, all I managed was a solder bridge across the first 3 pins that I couldn't get off well for fear of damaging the ASIC. I considered pulling all three up and splaying them on top of the ASIC, clearing the bridge, and then using jumpers to connect them, a technique I first used to reverse-engineer and tap the TI-83+ ASIC's keypad connections. However, I plugged in the battery, the calculator still booted, and DrDnar's CLOCK program revealed the calculator was still running at 6/15/15/15 MHz, so I closed up the calculator and called it a day.

Bottom line: overclocking this ASIC is really, really hard, and simply shorting pins together does nothing (fortunately, in my case). Don't try it.
Wow, thanks for the warning. That seems scary. I admit that as I was reading your post that I was getting increasingly stressed, hoping that you didn't break your calc.
Bummer that we can't overclock the one that actually needs it <_<
DJ_O wrote:
Wow, thanks for the warning. That seems scary. I admit that as I was reading your post that I was getting increasingly stressed, hoping that you didn't break your calc.
Yeah, it was pretty stressful to attempt, too. Smile Elfprince: agreed. I remain hopeful that I'll hear back from my TI contacts about my questions for unlocking the higher speeds during manufacturing and/or using an ez80 core, though.
If only TI and Casio had inspired themselves from HP in terms of processor choice and writing OSes. Although I am glad TI and Casio's OSes and connectivity softwares are far less buggy than the HP 39gII's, just take a look at how fast a BASIC-like language game can be on this calculator:



At 66 MHz with a 4-level grayscale 256x127 resolution, this is how fast it gets, and that's something considering the on-calc BASIC-like language lacks screen shifting routines. In low battery or USB mode (around 17-20 MHz) I get roughly 4 frames per second on this game. If I didn't have to redraw the entire screen every frame, I can't imagine how fast this game would run.

Now try to make such scrolling tunnel in TI-84+CSE BASIC or Casio PRIZM BASIC using no ASM library. The only upside you'll get is that the game code is over 10 times smaller and you'll be spared the many OS freezes.
KermMartian wrote:
I remain hopeful that I'll hear back from my TI contacts about my questions for unlocking the higher speeds during manufacturing and/or using an ez80 core, though.


It would be wonderful if you were able to convince them of such a thing. Unfortunately, that doesn't seem very likely. Sad
Art_of_camelot wrote:
KermMartian wrote:
I remain hopeful that I'll hear back from my TI contacts about my questions for unlocking the higher speeds during manufacturing and/or using an ez80 core, though.


It would be wonderful if you were able to convince them of such a thing. Unfortunately, that doesn't seem very likely. Sad
It all comes down to what can be properly justified as something that will make a serious impact on the experience of students and teachers who use the calculators. For example, an ez80 will let graphing be about 4x faster, but the question is if teachers and students actually want faster graphing or not.
One thing for sure, students who write programs or notes will find the missing keypresses and slow scrolling issue annoying when using the program editor, same when scrolling down through menus.
DJ_O wrote:
One thing for sure, students who write programs or notes will find the missing keypresses and slow scrolling issue annoying when using the program editor, same when scrolling down through menus.
I think it's most noticeable in the program editor as opposed to normal menus, but it's definitely a big pain in the neck. I wish I had demonstrated the program menu typing speed during my meeting at T^3; I forgot about that detail.
KermMartian wrote:
It all comes down to what can be properly justified as something that will make a serious impact on the experience of students and teachers who use the calculators. For example, an ez80 will let graphing be about 4x faster, but the question is if teachers and students actually want faster graphing or not.

As a student who has used both an 83 Plus and an 84 Plus SE, I say by all means have faster graphing! It makes my life so much easier especially when I'm setting up complex equations. However, I don't think that TI will end up getting actual feedback on this because this is the sort of thing that people don't realize they want until they taste the difference, just like foods, OSes, cars, Technicolor, etc. Which is quite a diabolical move on TI's part, since they don't have to change.
Although I can't cite my source on this, one person mentioned that many teachers actually like the slower graphing, as it makes students think about how the y value of a rectangular function (for example) changes as the x value increases. That's purely anecdotal, of course.
@DJ_O: That is fairly awesome speed, especially considering that it is in a BASIC language and you cannot shift the screen.

KermMartian wrote:
Although I can't cite my source on this, one person mentioned that many teachers actually like the slower graphing, as it makes students think about how the y value of a rectangular function (for example) changes as the x value increases. That's purely anecdotal, of course.

It wouldn't be difficult to add in a delay, though, for teachers that want to slow down the graphing. I am pretty sure graphing doesn't need to be nearly as slow as it is.
Xeda112358 wrote:
KermMartian wrote:
Although I can't cite my source on this, one person mentioned that many teachers actually like the slower graphing, as it makes students think about how the y value of a rectangular function (for example) changes as the x value increases. That's purely anecdotal, of course.

It wouldn't be difficult to add in a delay, though, for teachers that want to slow down the graphing. I am pretty sure graphing doesn't need to be nearly as slow as it is.
Yeah, I feel like the fairly obvious answer to this is: Once the students get that, they're going to want fast graphing. Adding a toggle-able delay would be ideal, I think; that's basically what the asymptote checking is, anyway.
Hey, will you please post a tutorial/more detail about this so we can try this ourselves?

I really want to do this.
pimathbrainiac wrote:
Hey, will you please post a tutorial/more detail about this so we can try this ourselves?

I really want to do this.
What kind of calculator do you have, and which ASIC version? How much soldering experience do you have?
  
Register to Join the Conversation
Have your own thoughts to add to this or any other topic? Want to ask a question, offer a suggestion, share your own programs and projects, upload a file to the file archives, get help with calculator and computer programming, or simply chat with like-minded coders and tech and calculator enthusiasts via the site-wide AJAX SAX widget? Registration for a free Cemetech account only takes a minute.

» Go to Registration page
Page 1 of 3
» All times are GMT - 5 Hours
 
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum

 

Advertisement