Max RAM for Linux only 1GB?

John Whitney john.whitney at
Sat Nov 1 04:28:55 EST 2003


The easiest route it to turn on highmem support (CONFIG_HIGHMEM).  As far as
I know, this does work for the PowerPC.  My understanding is that the kernel
doesn't directly use this memory, but will allow user-space programs to use
it (mapped into their memory space), which should in turn free up the memory
the kernel DOES use.

I think you'll need to start playing with the kernel start address if you
want the kernel to benefit directly from the additional memory.  I know this
has been done successfully to 0xA0000000, not sure about all the way down to
0x80000000 (but I can't think of why it wouldn't off the top of my head).


On 10/31/03 11:58 AM, "Prakash Kanthi" <pkanthi at> wrote:

> Folks,
> I have over 1GB DIMM RAM on my board running PPC 405.
> How can i ioremap that to my OS? As Linux virtual
> space starts at 0xC0000000, we have only 1GB more for
> all virtual space mappings.
> Even if i move 0xC0000000 to 0x80000000, what will
> happen to TLB settings? Any problem there to map 1GB
> additional RAM?
> Any idea as to how i can do this?
> Thanks,
> Prakash

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