XBOX360 CPU JTAG port J8C1

XBOX NAND rad/write.
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d0
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XBOX360 CPU JTAG port J8C1

Post by d0 »

If an exploitable 360 was flashed with a downgrader image, and downgraded to kernel 1888 would the xbox then open the efuse that disables the CPU JTAG port from becoming functional. I heard somewhere that the first efuse blown with the first update prevents access to this port, but will downgrading the kernel back to 1888 original allow access to this CPU JTAG port? and will USB JTAG NT Support this in the future if it was possible? i know that admin has an XBOX capable of being downgraded to kernel 1888 because i'm the donater and it is an Xenon..
hutiu
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Post by hutiu »

Once the efuse is blown, that is the end of the current jtag exploit.
d0
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Post by d0 »

im not talking about the current JTAG exploit eFuse, i mean the CPU JTAG Port J8C1, you see every whenever the 360 is updated the XBOX 360 blows a diffrent eFuse. My question is if on an already JTAG exploitable console, you perform a Downgrade to the original kernel version would the CPU JTAG port J8C1 become usable, and how it would be beneficial, ex. reading out CPU key - Downgrading etc,
hutiu
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Post by hutiu »

From my understanding about efuses, is that once they are blown, they are gone. You would have to manually get inside the CPU and "reconnect", if you will the blown fuse.
fox_el_negro
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Post by fox_el_negro »

before the jtag is done. remove t rt6 below the cpu, this prevent to blow the fuses!!!!!
boarder1042
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Post by boarder1042 »

ak4d7 wrote:If an exploitable 360 was flashed with a downgrader image, and downgraded to kernel 1888 would the xbox then open the efuse that disables the CPU JTAG port from becoming functional. I heard somewhere that the first efuse blown with the first update prevents access to this port, but will downgrading the kernel back to 1888 original allow access to this CPU JTAG port? and will USB JTAG NT Support this in the future if it was possible? i know that admin has an XBOX capable of being downgraded to kernel 1888 because i'm the donater and it is an Xenon..
Optional: Remove R6T3 resistor. Not for the average user, the resistor is small and difficult to handle, you may damage your XBox.
Blowing a new fuse is not a problem, but if you plan to upgrade several time for experiments and you wish to remove it do so with care.

taken from iDowngrading_the_xbox360_v1.1.doc on xbins
macanazo
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Post by macanazo »

i have an xbox with a 8.x.x.x dash, is it screwed for now?
crazie
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Post by crazie »

macanazo wrote:i have an xbox with a 8.x.x.x dash, is it screwed for now?
Not for now, try forever.. There is no way that M$ will reopen the door to the security hole that was used for the exploit. And since the code is roughly 200 lines or something, it is pretty much never gonna happen..
gone
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Post by gone »

So with an 8.x.x.x dash, jtagging no longer possible. But this doesn't effect the ability to flash DVD drives to play my backups right?
aznhacka
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Post by aznhacka »

gone wrote:So with an 8.x.x.x dash, jtagging no longer possible. But this doesn't effect the ability to flash DVD drives to play my backups right?
yup yup you are correct
gone
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Post by gone »

Thanks. I'd picked up two units and put them online about a week before I started reading about the live bans. So, of course they took updates.
boarder1042
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Post by boarder1042 »

How would you go about reading the cpu key if the efuse isnt blown?

When m$ updates the dash again it will open another efuse.
cc17926
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Post by cc17926 »

i know im probably reviving an older topic, however this would probably be the best spot to post my question. in regards to the e-fuse being blown to the jtag port (if this is whats exactly blown).. would something stop someone from using an over-the-top flash programmer to read, modify the code, then reprogram the chip ? also, what is this all about a cpu key?? thanks for any details!
d0
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Post by d0 »

It's the first eFuse that disables this jtag port and its done at production. If a CPU {eFuses blown} is removed and replaced with a brand new from factory CPU {all eFuses}, would it activate J8C1? This port has a function, maybe it talks directly to the CPU/NAND/XSB. Probably the only people who know about it and how to access it work for MS, who use it to recover the CPU/DVD key at the Repair centers.
cc17926
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Post by cc17926 »

well.. can't the flash (nand?) be read from over-the-top of the chip using special tools, instead of just using traditional jtag ?
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