The link looks... interesting. 
I bet it looks even more interesting right now :
(gdb) x/16x 0x30000000
0x30000000: 0x30000020 0x00000000 0x00100000 0x30000000
0x30000010: 0x00100000 0x004a3556 0x36313432 0x00000000
0x30000020: 0xeb000000 0xeafffffe 0xe92d4008 0xe59f000c
0x30000030: 0xeb00017f 0xe59f0008 0xeb0001cc 0xeb00012b
(gdb) set *(unsigned) 0x30000000 = 0x12345678
(gdb) x/16x 0x30000000
0x30000000: 0x12345678 0x00000000 0x00100000 0x30000000
0x30000010: 0x00100000 0x004a3556 0x36313432 0x00000000
0x30000020: 0xeb000000 0xeafffffe 0xe92d4008 0xe59f000c
0x30000030: 0xeb00017f 0xe59f0008 0xeb0001cc 0xeb00012b
(gdb) x/4x 0x56000070
0x56000070: 0x1400150a 0x00000062 0x01554050 0x00000000
(gdb) I technically reached the minimum amount of features to one-up Lionel Debroux's PoC. I won't make an official announcement on the relevant board before Christmas for obvious drama and pun combo reasons, but if anyone wants to
mutilate their calculator experiment with this before then :
You need a way to connect to a
3.3v TTL serial port. Open up your Prime and connect said way to UART_RX, UART_TX (right on top of the flash chip on my model) and BAT-.
On Debian, install the required cross-compiler packages (binutils-arm-none-eabi gcc-arm-none-eabi gdb-arm-none-eabi), clone the repository, use make to build everything. Prepare a terminal emulator at 115200 bauds.
On Windows, replace PRIME_OS.ROM with ripem.rom, connect the calculator to the computer (the battery isn't required - the Prime can power itself from USB), flash the new OS.
Back on Debian, check that the traditional "Hello world!" appeared on your screen. Close the terminal emulator and use arm-none-eabi-gdb to poke around.
And as always : please void your warranty in a responsible manner, I take no responsibility for whatever you did to your poor calculator.
