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Re: about PXE net boot.

From: Yoshinori K. Okuji
Subject: Re: about PXE net boot.
Date: Fri, 01 Feb 2002 23:32:44 +0900
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At Fri, 1 Feb 2002 13:46:03 +0100,
Rui Zhu wrote:
> So my first question is what the magic number 608 means (I have no
> experience of real mode). Second, might someone have some idea how to
> solve such problem?

For the first question, it is derived from (0x90000 + 32K). 0x90000 is
the traditional address where Linux's real mode code is loaded. 32K is
the maximum size of the code. So (for older kernels) at least 608K is

For the second question, I think two things should be done
(potentially). One is to free the memory used by a PXE ROM. Because
GRUB doesn't use PXE even in the case of being loaded by a PXE ROM (at
the moment), GRUB should uninstall PXE code right after being
loaded. This must enlarge available memory space.

The other is to add support for relocation of Linux real mode
code. According to the Linux/i386 boot protocol, you can do that with
a protocol version >= 2.00, but 2.00 and 2.01 require >576K to pass a
command-line string, because it is not relocatable with these
versions. In 2.03 or above, you can even put a command-line string
arbitrarily. The reason why I didn't add support for that is just that
it was complicated to support various versions simultaneously.


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