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What is the difference between MMU and MPU?

Discussion in 'Embedded' started by Neworks, May 13, 2004.

  1. Neworks

    Neworks Guest

    I don't really know the difference between MMU and MPU. Could anyone
    give me a brief idea about it?
    Neworks, May 13, 2004
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  2. Whatsamatta you? Haven't figured out how to use Google to look
    up answers to homework questions?

    MMU == memory management unit

    It's a part of a CPU (or an external peripheral) that handles
    things like memory segmentation and protection, virtual memory
    paging, etc. Basically it sits between the CPU itself and
    external memory and translates virtual memory addresses
    produced by the CPU into physical memory addresses and raises
    an exception when there isn't a valid mapping for the requested
    operation and address.

    MPU == micro processor unit

    The rest is left as an exercise for the reader...
    Grant Edwards, May 13, 2004
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  3. Neworks

    BiLL Guest


    As far as i know, MMU are more complex than MPU.
    MPU only offer access management over memory areas (depending on running
    level, some may be set not accessible), whereas MMU enables you to create
    virtual memory spaces.
    With MMU the logical mapping differs from physical mapping, and depending on
    the complexity of the MMU it may be possible to make a fragmented set of
    memory chunk look like a continuous area, or do some swapping with mass
    storage device. MMU also checks access stay within defined context limits.
    The little drawbacks for MMU are quite bigger memory description tables and
    maybe some increased access delay, power consumption and costs.

    hope this will help!

    BiLL, May 14, 2004
  4. Neworks

    BiLL Guest

    I assumed you were talking about Memory units
    I went across a MPU concept, as memory protection unit, while working on
    secured microcontrollers for paycard systems

    sorry if the real question was processing unit vs. memory unit.

    BiLL, May 14, 2004
  5. Sometime also

    MPU == Memory Protection Unit

    Handles only memory protection and often is limited to a few regions.
    42Bastian Schick, May 14, 2004
  6. Neworks

    Pete Fenelon Guest

    He's a bright lad, by the standards of the usual homework bums. He's
    even posted through posting.google.com so we can't find out which college
    he's at ;)

    Pete Fenelon, May 14, 2004
  7. Just in case anybody missed the joke, "Whatsamatta U." was
    Bullwinkle Moose's Alma Mater. Don't know if they had a EE
    program there...
    Grant Edwards, May 14, 2004
  8. Neworks

    Joe Guest

    Memory Protection Unit prevents a user application from accessing memory
    regions own by OS.

    Memory Management Unit can do the same thing, but it also provide
    virtual memory (mapping of logical memory to a physical memory based on
    memory base offset defined by OS). In this way, a user program don't
    have to be loaded into a fix location in the main memory. It can be
    loaded and execute from anyway in the system memory, and the MMU can do
    the memory translation during program execution.

    Joe, May 16, 2004
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