Protecting eFuses and JTAG From Updates (R6T3, U6T1, U6T2 Methods)
If you are lucky enough to have a JTAG'd Xbox 360 then it is recommended that you protect your CPU fuses (known as 'eFuses'). If you do not do this and accidentally update with an official MS update via disc etc you will lose the ability for your XBOX 360 to run unsigned code - therefore no FreeBoot, XBR etc., thus rendering the JTAG hack useless.
The process is quite simple and involves either removing a resistor or bridging a small gap. You can choose either method, it's really which ever you feel the most comfortable with. I personally bridge the gap as its easily reversible, but that just me.
First you need to remove the Xbox 360 motherboard from the case. On a side note if you are going to do this, you may as well fit an XClamp fix kit. There are many methods of doing this, however my personal favorite is the Xecuter RROD Repair Kit Pro II.
1. Removing the R6T3 Resistor
Source:
http://www.free60.org/R6T3
R6T3 is the label of a resistor on the underside of the 360 motherboard. of the Xbox 360. It supplies the necessary voltage for the CPU to burn the so-called e-fuses. Burned e-fuses prevent older firmwares (currently any older rev. than 4552) from running on your Xbox 360, thus eliminating the possibility to downgrade to an earlier version of the kernel. It is a 10k Ohm (10,000 Ohm) SMT resistor (Case 0402) functioning as part of a current limiting circuit.
Important Note:
- The removal of R6T3 will cause an E80 system error if the NXE (2.0.12611.0 and above) update is installed.
- Replacing the resistor with the original or with another 10K Ohm resistor usually fixes the error state.
- Given the difficulty in surface mounting a resistor as small as R6T3, simply holding a 10K Ohm in place while the 360 is powering up after giving an E80 will typically allow normal operation from then on.
- Care must be taken not to bridge the R6T3 gap without a resistor in place as this may cause system damage.
XBReboot has virtual e-fuses, and will boot fine with the R6T3 resistor removed.
2A. Alternative Method: If UT61 is installed (Xenon & Early Falcon).
As a safer and easier alternative to removing the R6T3 resistor you can instead bridge two solder points on the underside of the 360 motherboard. This will prevent any accidental updates blowing eFuses. It can also be reversed very easily should you ever want to revert to an original Microsoft dashboard. I've used this method on several boxes so far and find it much quicker than removing the resistor. Credit goes to Blackaddr over on
xboxhacker for this alternative method (original thread
HERE).
2B. Alternative Method: If UT62 is installed (Late Falcon, Zephyr, Opus & Jasper)
Note: There have been some reports that soldering the bridge causes E79 on Zephyr motherboards so we would recommend removing R6T3.
Xenon and Falcon boards differ from late model Falcon, Zephyr, Opus & Jasper motherboards. You will find on late model Falcon and Jasper that U6T1 is not installed and UT62 is actually installed. The bridging process is the same and the diagram shows the difference clearly. Thanks again to Blackaddr.
