4MB DRAM is enough for linux kernel 2.2.13

4MB DRAM is enough for linux kernel 2.2.13

[Prashant Patel]

Hello Everybody
        Can someone tell me if 4MB DRAM is enough to boot linux kernel
2.2.13. Note that the 8xx rom boot loader occupies around 500k.

Thanks
Prashant Patel


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Re: 4MB DRAM is enough for linux kernel 2.2.13

[Dan Malek]

Prashant Patel wrote:
>
> Hello Everybody
>         Can someone tell me if 4MB DRAM is enough to boot linux kernel
> 2.2.13. Note that the 8xx rom boot loader occupies around 500k.

Yes, I can say it will not work.

The code in the arch/ppc/mbxboot directory, which is used for
all 8xx and 8260 processors, assumes there is memory above 4 MB
it can use for buffer space while decompressing the kernel.  You
can play around with adjusting these addresses and sizes, and get
a kernel to boot.  You will get a shell prompt, and that is about
all.  You won't be able to use a ramdisk, you probably won't be
able to execute any useful programs.


	-- Dan

--

	I like MMUs because I don't have a real life.

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Re: 4MB DRAM is enough for linux kernel 2.2.13

[Jari]

Hello,
I'm a newbie. Help me!!!!!
Can anybody tell me the minimum size of the linux kernel 2.2.13  that we can
reduce?
(this kernel doesn't need console, anything else ... just boot and run my own
program)
If I want to support only ftp, what is the minimum size of ramdisk ?
I think if I reduce the code of the kernel and the library libc6, 4MB is OK.
Is that right?
best regards,
Jari

ps: Hi Dan "grandfather of all of these", you wrote:

>         I like MMUs because I don't have a real life.

How old are you in this life?
I've just had my full-month celebration.  ;-))) just relax....





Dan Malek wrote:

> Prashant Patel wrote:
> >
> > Hello Everybody
> >         Can someone tell me if 4MB DRAM is enough to boot linux kernel
> > 2.2.13. Note that the 8xx rom boot loader occupies around 500k.
>
> Yes, I can say it will not work.
>
> The code in the arch/ppc/mbxboot directory, which is used for
> all 8xx and 8260 processors, assumes there is memory above 4 MB
> it can use for buffer space while decompressing the kernel.  You
> can play around with adjusting these addresses and sizes, and get
> a kernel to boot.  You will get a shell prompt, and that is about
> all.  You won't be able to use a ramdisk, you probably won't be
> able to execute any useful programs.
>
>         -- Dan


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Re: 4MB DRAM is enough for linux kernel 2.2.13

[Graham Stoney]

Jari writes:
> Can anybody tell me the minimum size of the linux kernel 2.2.13  that we can
> reduce?   (this kernel doesn't need console, anything else ... just boot and
> run my own program)

It's not so much the kernel you need to worry about, it's the root file system
containing the runtime libraries that take up most of the space.
Nevertheless, I have some kernel minimisation patches available at:
    http://members.nbci.com/greyhams/linux/patches/2.2

> If I want to support only ftp, what is the minimum size of ramdisk ?
> I think if I reduce the code of the kernel and the library libc6, 4MB is OK.

As Dan said, you won't fit a ramdisk in only 4Mb.  You would need to use a
(probably compressed) flash filesystem; others have done it, but is it worth
the hassle given that RAM is cheaper anyway?

You can find more info about this in the HOWTO at:

http://members.nbci.com/_XMCM/greyhams/linux/PowerPC-Embedded-HOWTO-3.html#ss3.2

Regards,
Graham
--
Graham Stoney
Principal Hardware/Software Engineer
Canon Information Systems Research Australia
Ph: +61 2 9805 2909  Fax: +61 2 9805 2929

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