Alot of people seem to be confused about this, so here you go
The Matrix chip is essentially the same as a cheapmod, and like the cheapmod it will not work on 1.3, 1.4, 1.5 boxes because access to the lframe signal has been removed. There is a way to access lframe signal, but it requires soldering to a very small point on the nvidia chip. I RECOMMEND GETTING A NEWER MOD CHIP THAT DOES NOT NEED LFRAME CONNECTION. But it is possible I have done it on a 1.4 box.
You need to remove the d0 pogo pin (heat up the solder and it will slide right out), I have found that the remaining pogo pins will slide down tightly into the holes on the header making great contact. I used a thicker washer between the matrix and the mobo. Or you might want to remove all the pogo pins and hardwire it.
1. Connect a wire from the matrix d0 to the moved d0 point:
or the alternate d0 on the bottom of the mobo:
2. Connect a wire from the d0 on the matrix to ground (pin 2 on matrix or a screw)
3. Now the TRICKY part, connect a wire from the alt lframe point on the nvidia chip to pin 3 on the matrix. I used a small flathead jewelers screwdriver to gently scrape the point until I could see metal, I then used solid copper wire(phone wire) wrapped around the tip of my cheap soldering iron to solder the connection, the wire made a nice very small tip which made it much easier to solder without doing any damage, someone else has reported success using a "radio shack 15 Watt Pen soldering iron"
WARNING: YOU CAN PERMANENTLY DAMAGE YOUR XBOX TRYING TO MAKE THIS CONNECTION, YOU HAVE BEEN WARNED
Once you have it connected, tape or glue it down as it will come off very easily, I used electrical tape, make sure you cut away any tape from the top of the nvidia chip as it may cause it to overheat, adding a heatsink is probably a good idea too
on a 1.5 box you must also connect matrix pin 2 to ground, and pin 9 to 3.3v
IMPORTANT: Make sure you have a recent bios loaded on the matrix, older bios will not work on a 1.4 or 1.5 box
And don't blame me if you fry your box