How Does a Jtag physicly work?

[teknogod17]

So I cant seam to figure out how a jtag workes. I know that a rgh chip sents a pulse to the cpu wich glitches it into reading the hacked nand but how does a jtag make it read a hacked nand. How does 2 diodes make a xbox do this.

 

[professor_jonny]

I think the two diodes tell the smc to inject the payload into memory in a basic way of thinking.
before the diodes and smc hack it required sending the payload via debug using the king long expliot.

The glitch expliot resets the cpu to pass verification of the hacked nand not to load the hacked nand, it envokes a hardware glitch in the cpu.

 

[David Watters]

heres some good reads on it

http://www.maxconsole.com/maxcon_forums/threads/151422-Jtagging-Explained

http://www.securityfocus.com/archive/1/461489/30/0/threaded