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Re: Why does Linux need memory management units and cache?

Cross-posted to 3 groups.

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On 05/19/2012 07:34 PM, 7 wrote:
[...]
> Virtual address space in a nut shell means program counter relative
> operation. So if I were careful to keep supervisory
> programs separate from user programs, and manage my address
> space of user programs with PC relative addressing,
> I won't need memory management hardware. All I need is a
> fast program that keeps the virtual memory management functions
> going because that should still be faster than setting up MMU
> and managing its operations.

Actually, that's more or less what Amiga was doing
and many Real Time OSes.

It is faster, also faster to crash, since programs
could, -intentionally or unintentionally-, address
memory which they should not.

> So a cache could be implemented in software. And if done properly

I doubt it is possible, unless the CPU supports such
things, having, for example, some scratch pad RAM.

Since cache is cache, i.e. fast but small memory, it
has to be an hardware component.
How this hardware is handled, is CPU dependent.

bye,

-- 

piergiorgio

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Why does Linux need memory management units and cache? 7 <email_at_www_at_enemygadgets_dot_com@enemygadgets.com> - 2012-05-19 13:40 +0100
  Why does Linux need memory management units and cache? Kulin <remailer@reece.net.au> - 2012-05-19 14:26 +0000
  Re: Why does Linux need memory management units and cache? Niklas Holsti <niklas.holsti@tidorum.invalid> - 2012-05-19 19:40 +0300
    Re: Why does Linux need memory management units and cache? 7 <email_at_www_at_enemygadgets_dot_com@enemygadgets.com> - 2012-05-19 18:34 +0100
      Re: Why does Linux need memory management units and cache? Piergiorgio Sartor <piergiorgio.sartor.this.should.not.be.used@nexgo.REMOVETHIS.de> - 2012-05-19 19:44 +0200
        Re: Why does Linux need memory management units and cache? 7 <email_at_www_at_enemygadgets_dot_com@enemygadgets.com> - 2012-05-19 19:57 +0100
          Re: Why does Linux need memory management units and cache? Piergiorgio Sartor <piergiorgio.sartor.this.should.not.be.used@nexgo.REMOVETHIS.de> - 2012-05-19 21:17 +0200
            Re: Why does Linux need memory management units and cache? 7 <email_at_www_at_enemygadgets_dot_com@enemygadgets.com> - 2012-05-20 22:53 +0100
      Re: Why does Linux need memory management units and cache? Grant Edwards <invalid@invalid.invalid> - 2012-05-20 14:42 +0000
        Re: Why does Linux need memory management units and cache? Hadron<hadronquark@gmail.com> - 2012-05-20 16:48 +0200
          Re: Why does Linux need memory management units and cache? Nix <nix-razor-pit@esperi.org.uk> - 2012-05-20 22:19 +0100
            Re: Why does Linux need memory management units and cache? 7 <email_at_www_at_enemygadgets_dot_com@enemygadgets.com> - 2012-05-20 22:55 +0100
              Re: Why does Linux need memory management units and cache? Nix <nix-razor-pit@esperi.org.uk> - 2012-05-21 16:24 +0100
                Re: Why does Linux need memory management units and cache? chrisv <chrisv@nospam.invalid> - 2012-05-21 10:44 -0500
                Re: Why does Linux need memory management units and cache? GreyCloud <mist@cumulus.com> - 2012-05-21 10:51 -0600
                Re: Why does Linux need memory management units and cache? GreyCloud <mist@cumulus.com> - 2012-05-21 10:51 -0600
                Re: Why does Linux need memory management units and cache? Foster <frankfoster50@yahoo.com> - 2012-05-21 12:53 -0400

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