You can read the how here. It talks about the development process, code, and how modified Xboxs can be utilized.

A link to the GitHub page can be found here. The information below is from the read me section.

Features

This mod adds the following features to the game:

• Support for 480p (proper), 720p, and 1080i (1080p) resolutions.

• Triple buffering support to increase FPS performance.

• Utilizes extra RAM if you have 128MB RAM upgrade.

• GPU overclocking for performance improvements.

• Increased HDD transfer speed for faster load times.

• Customizable field of view.

• Customizable split screen divider (horizontal or vertical).

RAM Upgrades

If your console has 128MB of RAM this patch will utilize the extra RAM available which will enable use of 720p and 1080i video modes as well as increase the size of in-memory caches for textures and geometry. The size increase for the texture and geometry caches will significantly reduce pop-in issues to the point of being almost non-existent.

GPU Overclocking

In order to maximize performance of the game when running in higher resolutions I’ve added support to overclock the GPU on startup. This is customizable and can be fine tuned to better suit each console’s unique GPU qualities. This is highly recommended for 720p mode as it can increase FPS by as much as 10 FPS. However, overclocking the GPU comes with risks and precautions should be taken to ensure you don’t cause your GPU to overheat and burn out. The risks are outlined in the wiki and should be thoroughly read and understood before attempting to enable and configure GPU overclocking. HDD Transfer Speeds

This patch can increase the speed at which the HDD transfers data to the console which will improve loading times and help reduce pop-in. This value is customizable via the config file and is explained in detail here. In order to use transfer speeds faster than UDMA 3 you will need an 80-pin IDE cable. Trying to use UDAM 4 or 5 with the stock 40-pin cable will result in read errors and the game crashing on startup.

Quality of Life Improvements

A few quality of life improvements have been added such as customizable field of view and options to control whether split screen divides the screen horizontally or vertically.

Compatibility

Due to how this patch works it is not compatible with the Xbox 360 back-compat emulator, nor will it ever be. It would require complex changes to the emulator itself and I have no plans on ever investigating it further. This patch has also not been tested on XQEMU or any other Xbox emulator for PC. It has only been tested on real hardware and I have no plans for providing additional support for any other means of running original Xbox games.

Hardware Requirements

This patch can be used on any soft or hard modded Xbox console with no additional hardware modifications. However, if you don’t have the 128MB RAM mod you will only be able to play the game in 480p mode. There is NOT enough RAM to play the game in 720p or 1080i without the RAM upgrade. Additionally you will need an 80-pin IDE cable if you want to use HDD transfer speeds faster than UDMA 3. You do not need a CPU upgraded console to use this patch and having one does not provide any additional performance gains that I’ve been able to measure during testing.

Known Issues/Limitations

This patch currently only works with the base version of the game (1.0) and does not work with the 1.5 update. I plan to port the patch to the 1.5 update at some point in the future. In addition to that there are a couple limitations/known issues such as:

• Campaign checkpoints may not work between this patch and other versions of the game. When loading a campaign save game you may have to start the most recent level from the beginning instead of from the last checkpoint reached.

• You will not be able to take screenshots using Xbox Neighborhood or other tools based on Xbdm when running with 128MB of RAM. You will need to use a tool I wrote that can handle taking screenshots when using 128MB of RAM: XboxImageGrabber

• HUD elements will get smaller when using higher resolutions. Scaling the HUD elements is non-trivial and will most likely not be fixed.

• Bink videos (intro, attraction, credits) still play in 640x480 resolution. I may look into fixing this in a future update but will most likely result in the videos being stretched.

• Campaign loading screen, player sign-in screen, and pre-game lobbies still render in 640x480, adjusting this is non-trivial and most likely won’t be fixed.