Re: Low memory on Virtex-II Pro

On Fri, Feb 07, 2003 at 02:56:30PM -0700, Kerl, John wrote:

Hello all,

There have been some recent posts about Linux & Virtex-II Pro
(FPGA with PPC405 hard core).  & apparently people have it working.

One question before I start, though:

Of course the kernel starts at *virtual* address 0xc0000000, regardless
of the processor.  But my understanding is that certain processors have
zero-based *physical* addresses for RAM, and some don't -- x86 of course
being an example of the former, and ARM being an example of the latter.
I believe that PPC is an example of the former.  Certainly our MPC857T
board, and all the other boards of which I'm aware, have RAM starting at
physical address 0x00000000.

The 405 has an exception vector pointer register, which is initialized
by linux (linuxppc_2_4_devel cvs tree) with the kernel base. So in
principle it should be possible to have linux run on a system without
memory at address 0. I have never tried this however.

Cheers,

Peter.


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