Casio-BANK recently published informations and tutorials on how to convert a FX-9750GII (not the original FX-9750G+) into a FX-9860GII. Despite the 9750GII only having access approximately 30 KB of RAM, it contains the same hardware as a Casio FX-9860GII, except the lack of a backlight, which features 1.5 MB of Flash memory and add-ins support (the equivalent of TI Flash apps). Unfortunately, the tutorial is only available in French, but if you understand this language or can translate it, then all information and tools needed to allow you to replace the calculator OS and unprotect it can be found here. Note that in France, a FX-9750GII is called a Graph 35+ USB and a FX-9860GII is called a Graph 75.

In 2009, Brandon Wilson allowed something similar with the TI-73 with Chameleon, which allowed you to turn your TI-73 into a TI-83 Plus with no RAM execution protection (the so-called 8192 bytes of ASM code limitation). Now on TI-BANK, there is a news article about the possibility to do the same thing with a TI-76.Fr and 82 Stats.Fr instead, although it will most likely require an hardware modification.

On some lower-end Casio series, the same OS and hardware is even shared across multiple models, allowing you to simply blacken out a spot on the motherboard using an HB pencil, transforming your calculator into a new one without replacing the OS.

Critor, the conglomerate...

Really nice tutorial. Now people can get high-end calcs and disguise them as low-end calcs.

And yes, their marketing sure is confusing, renaming their stuff so it looks like different and better. For the FX-9750GII and FX-9860GII, I'm sure it's for saving money, so they could manufacture them in the same line, strip off some features of one of them and release it as low-end and the other as high-end. I heard companies such as Intel and Nvidia does that sometimes. If you follow Nvidia news, you will often hear things about Nvidia renaming all their graphics cards in a confusing way.

The original discussion can be found here (in English): http://www.casiocalc.org/?showtopic=4959

Welcome here, cfxm.
And thank you for all your help.

Nice stuff cfxm. Does this means there are actually two ways to perform this?

It's the same way. We're using the same tools.
There is just an additional step on the french Casio models with the current pfxRecover version.

Ah ok, thanks for the clarification. Strange that french models requires such additional step, though.

Something with a different BIOS / Boot Code if I remember well.
Current pfxRecover version doesn't make the calculator enter in OS update mode.
You need to force that manually.

According to cfxm, it should be fixed in the next pfxRecover version.

Ah ok, thanks for the clarification. Strange that french models requires such additional step, though.

This is mainly because on an fx-7400GII/fx-9750GII starting the OS update procedure via LINK/Receive has to be hard-coded (due to missing syscall support on these devices) and this beta version of pfxrecover does not know the checksums of French models yet. However, Simon Lothar - who wrote the update utility - is already working on an improved version.

You can work around this problem by starting the OS updater via the calc's BIOS when it boots up. This can be achieved on all GII models by a special key combination. On older models you have to close P104 (which is the OS update contact) on the PCB while pressing the reset button.