Firmware signature verification

[Melab]

That would be an interesting hack. Maybe one could swap a custom processor that is compatible with it. FPGA maybe?

And what exactly is JTAG'ing?

[Orby]

That would be an interesting hack. Maybe one could swap a custom processor that is compatible with it. FPGA maybe?

And what exactly is JTAG'ing?

JTAG=Joint Test Action Group. It'd allow hackers to control code execution from the first instruction on up. Quite a valuable tool, if we could get it working in the field.

An FPGA-based SoC replacement (RAM, CPU, and GPU) would be interesting, but would not only be hell to implement (you'd have to recode, restructure, and recompile all of iOS, which is not open-source) but, of course, Apple would also sue whomever made a working processor back to the stone age for patent violations innumerate. Never mind FPGAs are far less efficient than even a PPC-architecture chip (and are really infeasible compared to i86_64 and ARM).

[Melab]

I was just looking at some pages comparing the A4 to Samsung's S5PC110A1 at maybe with some mods it could be swapped out with the A4. And as far Apple goes, they can shove it...until I'm slapped with a lawsuit

But in order for something like that to be successful I'd have to where the bootrom is located. On the A4 possibly?

[Orby]

I was just looking at some pages comparing the A4 to Samsung's S5PC110A1 at maybe with some mods it could be swapped out with the A4. And as far Apple goes, they can shove it...until I'm slapped with a lawsuit

But in order for something like that to be successful I'd have to where the bootrom is located. On the A4 possibly?

I don't even know where the instruction set ROM is on the A4 die (and it is on there). I haven't seen a schematic (and good luck trying to locate it on a physical chip). I don't think anybody without schematics can effectively separate the CPU from the GPU, never mind start isolating specific half-words of instruction set ROM.

Now... for the debug and AP connectors? I know positively nothing about anything of that sort.

[Melab]

The ARM Cortex A8 dies on Samsung's Hummingbird SoC and the Apple A4 are actually identical, so as far as the instruction sets go I don't believe iOS would know the difference.