Xbox Xcode decompiler

This tool is available under the GNU GPL - please see source
file boilerplate for details.

Please note I can accept no liability for hardware/software damaged or
destroyed as a result of following these instructions.

What does it do?
====================

This tool reads the Xcodes from an Xbox bios image, and prints them to standard
output in a format suitable for creating a Cromwell bios image.

Why do I need it?
====================

The Xbox hardware is initialised at system startup based on information
stored in the Xcodes of the bios.

On the 1.6(b?) series Xboxes, Cromwell does not set up the memory timings
and other hardware initialisation sequences properly.  This leads to system
instability and boot-time failures.  Some symptoms of this problem post-boot
are kernel oopses and panics, and SIGSEGVs of userspace programs.

One day, hopefully, the Xcodes used on the 1.6 Xboxes will be reimplemented
in a clean-room fashion by the Xbox Linux team.  However, this has not yet
been accomplished, and progress has been very slow.

Using this tool, you can build your own Cromwell bios image for your Xbox
using the Xcodes that are already stored in the Microsoft bios on your
system (and therefore, you are not infringing their copyright by obtaining
these from an illegal source).

Is it legal?
====================

I believe that the use of this tool should be legal, but I must draw your
attention to the fact that you *CAN NOT* distribute a Cromwell bios image
which contains the Microsoft Xcodes built in, as this infringes their copyright.

I am a software developer, not a lawyer, so if you are in any doubt as to
whether you are allowed to distribute things, please consult a lawyer.

How do I use it?
====================

You will need the following:

Cromwell CVS-HEAD source code tree.

	This can be obtained from the Xbox-Linux
	anonymous CVS repository.  Instructions for checking out the code are
	available here:

	http://sourceforge.net/cvs/?group_id=54192
	(module name is cromwell)

A Microsoft Xbox bios from your xbox (or at least, an Xbox of the same hardware
version).  You can read this out from your Xbox on a 1.6 xbox by booting into Xbox Linux, turning OFF your modchip, and reading the bios contents using raincoat (raincoat -r OUTPUTFILENAME will dump the bios to a file).

A working Linux C development environment (e.g. gcc).

This program.

Usage - Steps
====================

1)	Check out cromwell, and cd into the tools sub-directory.
	Type 'make' to compile xdecode (any errors, please report them to me)

2)	./xdecode -t
		PATH_TO_MICROSOFT_BIOS_IMAGE > CROMWELL_DIR/boot_rom/Xcodes.h

	(all on one line)

	This reads the Xcodes from the Microsoft bios image, and writes them
	into the file Xcodes.h which will be used when compiling Cromwell.
	(Obviously, replace the PATH_TO_MICROSOFT_BIOS_IMAGE with the full path
	to the Microsoft bios image whose Xcodes you wish to use, and the
	CROMWELL_DIR with the directory of Cromwell source eg. /tmp/cromwell).

3)	cd CROMWELL_DIR (again, replace this with the source dir)
	Type 'make'

	This should then generate a pair of Cromwell bios images in the
	CROMWELL_DIR/image directory (cromwell.bin is the 256k image, and
	cromwell_1024.bin is the 1024k image)

	If you have a modchip which requires 512k bios images, you can create
	this as follows:

	cd CROMWELL_DIR/image
	cat cromwell.bin > cromwell_512k.bin
	cat cromwell.bin >> cromwell_512k.bin

4)	Flash the resulting bios image to your modchip.  If you have a modchip
	with only bank, I recommend caution for now - if there is a mistake,
	and the resulting bios image fails to boot, you could end up having
	to replace your modchip.  For information about how to flash bioses
	to your modchip, please contact your modchip vendor.