Telling kernel how much RAM to use at boot time?

James Wilkinson james at
Wed Jul 21 16:34:47 UTC 2004

- - s r b - - wrote:
> I've read that Knoppix has a boot code (RAM=xxx I think) that tells the 
> kernel how much RAM is available. Does Fedora have anything like this?

It's a Linux kernel option. From
/usr/src/linux*/Documentation/kernel-parameters.txt :
        mem=nn[KMG]     [KNL,BOOT] Force usage of a specific amount of memory
                        Amount of memory to be used when the kernel is not able
                        to see the whole system memory or for test. 

> I have a 512MB DDR333 that has bad memory just over the 400MB mark. I'd be 
> happy to be able to run Fedora with this memory by telling it not to try 
> to access anything over 400MB.

So mem=400M should work for you. However, the BadRAM patch at would be better. This requires
patching and recompiling your kernel, but it allows you to ignore only
the dud memory cells and use all the good ones.

Hope this helps,


E-mail address: james@ | "Microwave oven?  Whaddya mean, it's a microwave    | oven?  I've been watching Channel 4 on the thing
                       | for two weeks."

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