2008-10-26 05:07:24     uclinux for NON MMU?

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2008-10-26 05:07:24     uclinux for NON MMU?

Benix Samuel (INDIA)

Message: 64203   


I come to know that uclinux is for non MMU processor. But blackfin has inbuilt MMU. Does this mean uclinux will not use the MMU and hence dont exploit caching etc.




2008-10-26 08:17:54     Re: uclinux for NON MMU?

Mike Frysinger (UNITED STATES)

Message: 64204   


the Blackfin does not have an MMU.  ignoring that, caching support does not require a MMU.


please review the documentation:





2008-10-26 22:47:58     Re: uclinux for NON MMU?


Message: 64211   


Quoted from the doc: http://docs.blackfin.uclinux.org/doku.php?id=presentations:uclinux-dist:intro


Blackfin has MPU.




Memory Management Unit are included in many general purpose processors available today, however in some low cost variants, they are not. The MMU serves two main purposes:


    Virtual addresses. Allows processes to run in their own virtual contiguous address space. No need for relocating process addresses. Possible to expand the address space of a running process. The MMU raises an exception when no physical address is available, making it possible to implement swapping to disk.

    Address protection Actually done by the Memory Protection Unit (MPU) available in most MMUs. Prevents processes from accessing unauthorized memory addresses.


    µClinux supports embedded processors which support :

    MMU (protection and virtual memory support),

    noMMU (no protection, no virtual memory) and

    MPU (memory protection, but no virtual memory support).