Re: Question on MMU

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On Fri, Sep 10, 2010 at 9:07 PM, randd <4randd@xxxxxxxxx> wrote:
On Fri, Sep 10, 2010 at 10:19:27PM -0400, Sri Ram Vemulpali wrote:
> Hi all,
>
>       I have a question on MMU. Memory management is used to segregate the
> memory between process and make sure no process steps on each other. Also,
> it provides abstraction to whole available memory in a conceptual way called
> virtual address.
> Now my question is, we can do all this in software, I mean simulate and map
> the virtual address to physical address not taking hardware support. Now why
> is the hardware unit MMU is given with processor. Is there any special
> reason. Please clarify. Thanks.
>
> Regards,
> Sri.

well, i dont think we can do this all in the software. hw support is
required. whole of the kernel code runs in virtual address space, if
processor generates an address,without mmu, how will it find the code
that is supposed to convert virtual addresses to physical addresses.
Not quite true I guess. There are ports of the linux kernel which are supposed to run on hardware without a memory management unit. Eg. uClinux.
Speed is the definitely one of the answers here. There may be more reasons as to why MMU is in hardware.

Venkatram Tummala

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