Xbox 360:Disabling the eFuse Burning Circuit
Electronic fuses, or eFuses, are tiny circuits embedded in the CPU. Like a fuse in a house circuit, an eFuse is a metallic bridge that, when exposed to too much power, physically burns out and is permanent. Every official dashboard update burns some eFuses, making a permanent record of what dashboard version you are currently on, and it will check this record to make sure that you aren't installing a dashboard older than the one you're currently on, making it impossible to downgrade.
Fortunately, with RGH/JTAG exploited consoles, NAND images made with XeBuild will skip the eFuse check and will not burn eFuses. Furthermore, you can disable the circuit responsible for burning eFuses, making it impossible for eFuses to be burned. This also prevents official updates from being installed, since they cannot successfully burn your eFuses, so it errors out.
Disabling the eFuse Burning Circuit
Two methods exist to disable the eFuse burning circuit. Both methods involve this area on the bottom side of the motherboard:
If UT61 is present, as shown in the diagram below, bridge the solder of the two pads in the red box. This process can be reversed in the future by unbridging the two points.
If UT62 is present, as shown in the diagram below, bridge the solder of the two pads in the red box. This process can be reversed in the future by unbridging the two points.
The second method to disable the eFuse burning circuit is to remove the R6T3 resistor (phat) or the R4R1 resistor (Trinity) on the bottom side of the 360 motherboard as shown below, ensuring that you don't bridge the two R6T3 pads together. This process is not as easily reversible as Method 1, as you would have to buy and solder on another 10k Ohm resistor in order to restore functionality to the fuse burning circuit.
- Note that if you are on an unmodded console running dashboard 12611, you will receive an E80 error if this resistor is missing.