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Intel Microcode

Discussion in 'Electronic Design' started by [email protected], Jun 27, 2007.

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  1. Guest

    I was taught in university that microcode was what "high level"
    assembly language instructions were hardwired to on the lower level.
    Such that "add eax, ebx" becomes something like:

    load eax into some internal ALU register
    load ebx into some internal ALU register
    tell the ALU to go into "add-mode"
    tell the ALU to do it's thing
    load the result from the ALU into the eax register
    increase the program counter

    or something similar. I know this is probably a lot more complex on
    modern processors, but anyway...

    Now, I know that it has been possible to update the microcode in Intel
    processors for a very long time. And this is where I get confused:

    Does this mean that an Intel processor can be totally changed with
    microcode updates? How much of, say, a Core 2 Duo is hardwired, and
    how much of it can be updated with microcode updates? And if microcode
    is changable, is it still as fast as if it was hardwired?

    I am confused :(

    Please help!

    /David
     
  2. MooseFET

    MooseFET Guest

    I think you will find that only parts of the microcode can be
    changed. Other parts are fixed.
     
  3. ThanderMaX

    ThanderMaX Guest



    I think LINUX kernel does this (if it has the damoen installed). Look
    in the source forge site for the code.
    only a few opcodes are available for update. but sometimes it needs to
    decrypt and then update (for protection :( )
     
  4. I think it may be fairly flexible in terms of what can be patched, but
    the memory for patching is limited. Good luck getting public docs on
    doing it, though. Accessing the docs at Intel was on a need-to-know
    basis when I last wanted (and asked) to look at them.

    Jon
     
  5. Matt

    Matt Guest

    man microcode_ctl
     
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