4 replies to this topic

[frankmar98]

I can't find where is the fx-9750GII backup battery. I understand that its memory is RAM, so there must be a backup battery.

 

I have took a look to the hardware manual, and it don't talk about this.

 

The classic fx-9750G has a CR2032 backup battery.

 

I'm worried about this, because in the case it would have flash memory it can cause a lot of problems like seen in the AFX series.

 

¿The calculator has 64KB RAM, flash (or maybe EEPROM)?

 

Thanks in advance

 

Regards

[TeamFX]

The fx-9750GA Plus is the last model utilizing a backup battery. It was launched in 2008 and replaced by the fx-9750GII in 2009.

All Casio calculators now save user RAM data on a NOR flash chip when you turn off the device. This NOR flash is a lot better than in those AFX days, allowing up to ten times more erase cycles. Two flash sectors are used for backing up RAM data and are written alternately. So both sectors must be malfunctioning until your calculator can no longer restore recent user data after a reset (either by pressing RESTART or by replacing batteries). Yet, it should still be working.

fx-9750GII hardware specs:
- 29 MHz SH-3 or SH-4A (mid 2011) CPU
- 512 kB RAM chip
- 4 MB NOR flash chip

[frankmar98]

Thank you very much! Is exactly what I wanted to know.

 

I think that backup battery is a better sistem. But, if the calculator can operate during 40 years or more like this, I'll give an oportunity to this backup sistem.

 

Regards

Edited by frankmar98, 26 June 2016 - 06:11 PM.

[TeamFX]

40 years is a very long period. I don't think that it will live so long. The flash chip may survive it but other hardware components will break earlier.

E.g., the fx-CG10 runs at 58 MHz and models produced between 2010 and 2015 have a weak PCB component somewhere near the reset circuit. I don't think those models will live longer than 10 to 15 years. If you overclock the CPU, these models could die within a few months or even weeks.

Btw, the fx-CG10 uses six flash sectors for backing up RAM data which are also written alternately.
 

[frankmar98]

For example, the fx-7000g was marketed in 1985, and today you can find a lot of working units on Ebay after 30 years of life.

 

I think that is very cool that a calculator could work forever

 

Thanks for your help!