So Casio not only switched to SH4 on the new models, they started to use the same CPU on all of them... makes sense, it must make reusing code and optimizing it much easier.

Are there reports of dead calculators, of those that run at 29 MHz with the SH7305?

I don't know of any SH-4A 29 MHz devices suddenly entering coma.

Maybe... someone should write an underclocking utility for the Prizm.

Utilities can overclock up to 94.3 MHz and underclock down to 3.6 MHz. I know of people who use their Prizm at about 40 MHz to save battery. Personally I find that too slow.
Pover can mess with some more clock settings.

Now, what Casio should do is using separate read-only (preferably mask ROMs) for their bootloaders (back in the 1990s, their calculators and digital organizers used this for the entire OS, and nobody died - everything was well tested. I guess they only need to test the bootloader and make it read-only), or at least make the first sectors of the flash chips on their calculators write-protected.
Also, they could implement dynamic clocking of the CPU of their calculators. Dynamic (under)clocking is actually a very good idea, as calculators tend to spend lots of time waiting for user input, during which time they could be running at a lower clock speed, saving battery and the components.

Hello everyone.
I'm not english but I came to this forum because I just had this problem on my CG20 after trying to shut down my casio it was freezing I put out my battery and then it never started up again.
I am so much disappointed : I have a math exam tomorrow and I will have to use my emergency calculator (old old old Ti)...

Really? That's two calculators of the same model (well, actually not, one is a CG 10 and the other a CG 20, but there's little difference) failing on the same day.

Do you remember which OS version your CG20 had installed?

Note to self: today, do not turn off my calculator.

It's the brand new 2.0 ... love it !

(I feel so bad about that ... I don't even know how to use the old Ti ...)

lraimbault, I hate to ask this if you have done it already, but have you tried putting new batteries in?

Unfortunately, I did... I've done everything I could but nothing worked to bring it back to life ....
I feel desperate !

Ok guys, as I live in France I must go to bed but I praying that you'll find a way before I wake up (I know it's impossible but ...)

Thanks for you help until now

(and sorry for my english ^^)

Well, as you may have noticed already, someone else today (but in the USA) experienced the same situation a few hours before you.

If you're going to have an exam tomorrow, the best you can do now is relax and bring the old TI calculator back to life, remember how it works and do some exercises with it. I'm afraid you may have to spend some time using it as a replacement. Then later you may contact Casio (Casio Europe, in your case) and see what can be done.

Just for reference, do you remember how much time has passed since you bought your Casio CG 20? (remember Casio calculators usually have three years of warranty, at least here in Portugal).

I think I have it for more than 3 years... Anyway I will contact Casio to see if they can help me with that ...

That's unlikely as I think the Prizm was announced in January 2011... less than three years have passed, so virtually (and assuming Casio gives three years of warranty on every Prizm they sell) all the Prizms are in their warranty period.

Maybe the ROM isn't dead. Did anyone try to enter the emergency OS update mode?


- Press [F2]+[4]+[AC/ON]+RESTART at the same time and hold all keys for a few seconds
- Then release the RESTART button (still pressing [F2]+[4]+[AC/ON]) and wait a few seconds
- Now press [9]
- And then press [x] (multiplication)


If the calculator's ROM isn't dead or the boot code damaged, the message OS ERROR should appear on the LCD.

@gbl08ma


I still believe this is mainly because the software is not optimized (just look at the Casio BASIC implementation).


This would make the whole development process more complex. Also, there is only a very small number of people messing around with their ROMs and destroying the boot code. They could, however, just lock some sectors on the ROM but as long as they are writing the device type ID and the serial number into the boot code area, they can't do this.

If you ask me, I prefer an open platform. Even if there is a risk of damaging the boot code, you can still fix it if you know where the problem is. As an example: The ClassPad 330 Plus OS 3.10.2000 update adds the serial number to the boot code area as they somehow missed this in the original OS 3.10.0000
You could call this insane, but Casio decided to do it and it worked.


I guess this is something for the high-end market and not for embedded systems as this may shorten durability of the other circuits (the MPU may handle it).

I have reasons to believe their prototypes/emulators ran at higher CPU clocks, and the program editor is a nice example of what is really slow at the default clock speed (also, opening and leaving eActivity, but that's because of the flash speed).


I bet the people who just had their calculators break today, did not mess with the ROMs other than for official OS updates. And yet the calculators broke when pushing RESTART, which if I remember correctly is even recommended in the user manual for when the calculator hangs and nothing else works.


Well yes, I'm not sure how well prepared this Renesas core and the associated components are for constant clock switching. And I have many, many embedded systems laying around which do dynamic clocking, and not just mobile phones... even my MP3 player does it. So it's definitely not a matter of being an embedded system or not.

I got a reply that pointed me to the service and repairs page on Casio waiting for a reply back about what to do.

Good luck; I hope they repair or replace it soon. It'll be very interesting to see if you get that "new" hardware revision gbl08ma got, and if it has the same set (and lack) of components as him.

I fear mine is quite unique in that aspect, and may suffer from a premature death due to the missing capacitors. But let's wait and see.

Hmm... well, I set down my PRIZM (which was off) and the off screen all of a sudden turned on. It didn't go away so I pressed the reset button on the back. Nothing happened. Does anyone know of anything to do besides the [F2], [4], [AC/on] sequence? Should I just send it back?

Considering gbl08ma's luck with the reset button, you probably should indeed send it back. Good luck.