Re: Image file too large for low memory
Hi,
On Tue, Feb 18, 2003 at 07:51:03AM +0100, Thorsten Sauter wrote:
> Hello,
>
> On Tue, Feb 18, 2003 at 01:04:55AM -0500, Owen B. Mehegan wrote:
> > Node: 00B0D0A42B88
> > DHCP...
> > TFTP............................
> > File transfer error: Image file too large for low memory.
>
> are you sure, that the error message means the memory for you laptop.
> How many ram is available in this beast? :)
>
> While playing with tftp and network boot, I'll got this error message on
> many machines (i386, 3com or intel nic). The machines have 32MB and up
> to 512 MB ram, so a small 1.44MB floppy should be small enough to fit
> into the memory.
Ah. Welcome to the lovely 16-bit boot process of Intel machines.
<lecture>
Intel boxes boot up in real mode, in which 8086-style addressing is
enabled. In this mode, you don't have 32-bit memory offsets, but rather
16-bit segment addresses that are shifted 4 bits to the left before
adding a 16-bit offset address, forming a 20-bit address.
In short, until something switches the CPU to protected mode that uses
segment registers in a wildly different fashion, software can only
address the first megabyte of memory. The PC normally has up to 640 kB
of RAM in that first megabyte; the rest contains part of your
framebuffer and some ROM. So that's all you can access during the boot
process.
</lecture>
So if the NICs boot ROM contains only real mode code, 1.44 MB will
indeed /not/ fit into memory. Try a bare bones kernel; 512 Kb should
definitely work.
Cheers,
Emile.
--
E-Advies / Emile van Bergen | emile@e-advies.info
tel. +31 (0)70 3906153 | http://www.e-advies.info
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