---------------------------------------- > Date: Thu, 31 Jul 2008 14:47:02 -0700 > From: [EMAIL PROTECTED] > To: [email protected] > Subject: Re: Any company ever publish software that mimics their CPUs > *exactly*? > > 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". > Bah, we just need computers that can go back in time and start calculating form the beginning of the known universe. I think I read a sci-fi book about that once although they only could go back to their creation date, and hence got smarter over time. Yeah, I'm basically posting this due to the sci-fi reference.
Gabe -- [email protected] http://www.kernel-panic.org/cgi-bin/mailman/listinfo/kplug-list
