On Thu, Jul 31, 2008 at 02:50:48PM -0500, Gabriel Sechan wrote:
Every ARM emulator accepts 32 bit instructions. 32 bits is "only" 4 billion.
I just need to compare the state of RAM, registers and CPU before and after a
32 bit instruction for a measly 4 billion of them!!! Maybe it would finish
overnight and so I could wake up with proof in hand!
Of course I'd have to do this for various initial states of CPU, RAM and
registers since hardware isn't stateless like HTML.
Sure. Now lets say we have 10 registers of 32 bits. Since we don't
know how they may effect state we have to try all combinations, that's
a mere 2^320 states per instruction, for a mere 2^352 total tests. Let
me know when they finish, and we can start testing ram configurations
:)
Why not make it even worse (and still realistic). The CPU has a
pipeline, so the instructions don't execute independently. With modern
non-strongly ordered memory, you have to check possibly large sequences
of instructions to make sure they do the same things with memory
interactions.
I think, generally once a "solution" requires more compute steps than
the size/age of the known universe it is safe to consider it
"impractical".
David
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