Team-xecuter.com posted more details about their XHM Project where they'll release all info/schematics and sourcecode that will allow you to make a homemade DVD patchmod for Xbox360:
The : XHM forum is now open - we will be posting the first release in there later today.
Here is some further information regarding the Samsung Drive and XHM Project >>
1 : OE is NOT needed for the Mediatek to run the FW and can be held low, although this isn't recommended.
2 : OE toggle`s evenly on average (I say average because it changes speed some times but NOT when there`s valid data)
3 : OE high and low last for 60ns each (valid data time`s)
4 : From OE high to next OE high is 120ns
5 : Data is valid 20ns after OE going low, although it doesn't really need OE at all
6 : The address is presented to the 39SF020AFW 40ns after OE high
7 : The address is held there and stable for 80ns
8 : Data lasts for 80ns
9 : There is data present in-between the "real" data so beware when trying to "test" data lines
10 : The Mediatek device runs the FW directly from the 39SF020A
11 : The Mediatek doesn't run the FW sequentially, it runs it by instruction
12 : The Mediatek device has an internal memory device that shares the same pin connections as data and address of the 39SF020A
13 : The Mediatek device has dual internal CPU`s and some memory
14 : The SX18AC (or upwards) running @50mhz has an instruction time of 20ns
15 : The SX18AC (or upwards) can be overclocked although it can patch the Samsung "on the fly" @ 50mhz 20ns
16 : The SX devices have a reduced instruction set which can easy be grasped in a few hours
17 : Any one with half a brain cell can learn the SX instruction set.
This source code is in its infancy and is by no means rocket science, Don't expect it to work 100% It's "homebrew" so tinker with it that's what its there for. We wrote it to show just how simple patching the 39SF020A is and prove that it CAN be done with a cheap and relatively slow device, easily within the grasp of anyone with a degree of technical savvy.
The device we chose was an SX18AC but you could use any of the faster SX devices, for instance the SX28AC, I am sure most "homebrewers" will have a few of these kicking around You will also need a resonator, We used a Murata 50mhz version (again from an old homebrew modchip project)
There is also a thread of interest over at xboxhacker.net that is worth a read. A coder who goes by the name of "Uberfry" has also started his own discussions on a homebrew project - please show your support here