A Brief History of the Xbox Modchip

Please consider this a working document, please email any corrections/dates etc to history@llamma.com.  This is more of a story, second hand knowledge passed on to me from others and like any story each time it is told it changes a little. The target of this is for the novice to give a brief overview of the last few years of modding/hacking and not intended to be true to the word in every detail, generalizations are made and terms are invented.  That being said, if there is something obviously wrong please do point it out!

    At some point Andrew "Bunnie" Huang began working on a doctoral thesis, he somehow wrapped into it back engineering the part of the data stream from the bios to the GPU.  Check his site or read the book to find out more.  This is around the time the first original bios and other firmware files from the Xbox motherboard became available. 

First Generation Modchips
    One could say the first "modchip" was the original TSOP, but the chip socketed to make it easy to flash and re-flash with experimental code.  Hackers found they could send off their old motherboards in a blaze of glory by using a flash utility to put code on the bios chip and remove it from the board and then solder it into the Xbox main board (HomeBrew Chips).  Soon the first 29 wire true modchips became available, like the homebrew these used the same pathways as the original bios chip, these chips like Enigmah, Extender or homebrew are referred to as first generation chips.  They wedge their way in, both block the onboard TSOP chip from loading and load their code in its place.  These chips were capable of being flashed with new code (homebrew could externally from the console) but they did allow you to flash the onboard TSOP after write enabling the Xbox mother board. This opened a new doorway, any new bios code desired could be loaded to the roomy 1MB of onboard flash.

Second Generation Modchips
    Some improvements were made from the 29 wire design and lowered the wire soldering count to 11 wires.  Another feature of this generation is that the chip could now be flashed with new code while connected to the console and without removing the chip.  These could also be installed with a disable switch which allows users to boot in modded mode or non modded mode. read more

Third Generation Modchips
    Soon someone discovered a secret, the LPC (Low Pin Count) header on the board could be used to load a bios with only 9 wires!  Who should be credited, how did they figure it out?  I'm not sure but Andy Green came out with a chip design taking advantage of this access.  The CheapMod so called because it can easily be made by the home hacker with a socket some wire and a programmer that could also be homemade.  The Original CheapMod was born, Viperman contributed a PCB design for both the programmer and chip to make it easy to assemble (PDF/Gerber).  Many chip makers jumped into action improving upon or just mimicking this design and many chips followed; the cyclone, ozxchip, xkiller, X-elixis, Aladdin-Universal (also called Xecutioner) (later the Aladdin Advance), ALX2+, ChipStation, Apple-X2.  Even the first solderless chip "the Matrix" was based on the CheapMod design.  This was a breakthrough now with few wires and easy install these modchips became a favorite of consumers.  They no longer allowed easy flashing of the onboard TSOP but who cares they are relatively cheap and its always nice to have your original bios to fall back on if something gets screwed up during flashing.

Fourth Generation Modchips
    Using the LPC header as the method for interrupting the original bios and loading a different one many manufacturers have built a variety of chips providing various features.  The most common feature throughout 4th gen chips is the ability to select from several banks of bios', this means that without re-flashing the chip you can power down, flip a switch and select one of 2-4+ of pre-loaded bios and use choose one to use during the next boot.  Why would you want this you ask?  Well it is a good method to use if you are testing an unproven bios but for the most part people find one bios they like and stick with it.  Most 4th gen chips also include external LED's or change the color of the eject button LED to give you some feedback about what bank you have selected, whether the chip is enabled or disabled etc.  

Software Exploits
    Using holes in the software on the Xbox itself hackers have been able to run unsigned code.  Usually this involves an adapter to allow the Xbox to access a standard USB flash or other media to upload the data from a

TSOP Flash