Re: Rom on HDD

[Ken Yap <ken@nlc.net.au>]

> I`d like to ask you, how to make rom botable from HDD.   I haven`t
>eproms, and i like to boot computers over the network, and i wouldn`t use
>floppies for booting. ( i read the mailing list, but there wasn`t any
>answer for question like this) .   I try to use masq and bootblk, but
>there isn`t descriptions how it works and what todo to boot rom image
>from hdd.  I tried to move  floppy  image (test floppy for testing rom
>image) to hdd, but it won`t work. I hope there is somebody who can solve
>this problem sucessfully. 

Masq and bootblk have different purposes.

Masq, like comboot, was intended to be a small 512 loader prepended
in front of .com images and written raw onto a floppy for testing
Etherbooting. Since then comboot has been simplified into floppyload so
that .rom images can be used instead of .com images. This got rid of
the need to support two image formats in the Etherboot build process.
So both masq and comboot are obsolete.

Why are .com images not supported anymore? Loading Etherboot under DOS
was never totally reliable because DOS may have configured the hardware
in a way that interferes with Etherboot, e.g. installed an EMS driver.
The most reliable way is to start with a cold machine.

Bootblk is a header that is prepended to an Etherboot image so that
it becomes a network bootable image and Etherboot can be used to load
another Etherboot image. This occasionally is useful, e.g. a friend
needed to test a newer version of Etherboot on a machine that had no HD
or FD but an earlier version of Etherboot.  I'll put a short README file
in this directory in the next release.

Coming back to your question, if you have a HD, then I assume you
have some sort of OS already on it. Why not just forget Etherboot and
use loadlin to load a Linux kernel. I realise this means you have to
transfer the OS image to the client first rather than have it on the
server. Perhaps someone with a desperate need for booting from DOS can
adapt or emulate what loadlin does for loading Etherboot. Loadlin does
all those things needed to provide a pristine booting environment:
flushes the smartdisk caches, undoes any memory protection, etc, all
those things that make trouble for booting .com images.

Perhaps you really don't have an OS on the hard disk and you're willing
to devote the whole disk just to loading Etherboot. This is the case
for those people wanting to use Disk On Chip with Etherboot (elthough
there are some wrinkles with that too, to do with what DOC does to the
BIOS entry points). You might be able to find or adapt a bootloader that
will load Etherboot's raw binary format.  Or maybe you can convert the
raw binary format to something suitable.  Maybe objcopy can do this,
I haven't looked. Failing that, you could write the HD equivalent of
floppyload, just copy 32kB following the boot sector to 0x1000:0 and
jump to 0x1000:6.  How would you get this onto your HD though?
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