On Thu, 11 Nov 2004, Tal Achituv wrote: > guy keren wrote: > > > > >after all, a single machine-language op-code is _always_ translated into > >the same command - no matter how you name the assembly-language mnemonic. > > OK. > > >as i said above, a machine-language opcode must have a single meaning. it > >cannot mean different things in different times (unless you have different > >_modes_ for the CPU, which cause it to interpret opcodes differently. i > >assume this is not the same when it comes to non-priviledged op-codes). > > > You got me confused. I'm familiar with assembly language, machine code, > and the way one is translated to the other. > BUT - I am uncertain about the different modes the CPU might be in. > > You implied in your response that only priviledged op-codes could have > double interpertations - Are you _certain_ about that?
sorry, didn't mean to confuse. i didn't say that this is what happens - i assume that it does not, but i see this as the only way, for the implementors of the CPU, if they ever wanted that, to have the same op-code represent two different commands. again, i think this is not the case - i just didn't want to say something for certain, without being sure about it. > It puzzles me too that there might be an option under-which 0x90 could > be decoded into something else than the normal XCHG AX,AX. afaik it > really causes the cpu to exchange AX with itself... :-) unless the CPU was optimized to not do an operation which is known to be meaningless... ..unless it has some other side effects (e.g. changing CPU's flags such as carry, flushing pipelines, or what-not). i hope i'm not causing more confusion now then i did before ;) -- guy "For world domination - press 1, or dial 0, and please hold, for the creator." -- nob o. dy ================================================================= To unsubscribe, send mail to [EMAIL PROTECTED] with the word "unsubscribe" in the message body, e.g., run the command echo unsubscribe | mail [EMAIL PROTECTED]
