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Extracting 'initial' Kernel From Rom Chip


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#1 Jeremy_

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Posted 20 August 2010 - 01:09 PM

My first question is, the author of a book I'm reading says the 'initial' kernel is stored in this ROM chip. My question is what does he mean when he uses the word initial? Is there more than one kernel?

Anyway, I know there are a couple ways to do this, but I wan't to monitor the I\O pins on the ROM chip because I will eventually need to monitor the North-South bridge BUS, and I think that this would be a good way to prepare for that. Also I don't have a double-solder iron.

How would I get all these pins hooked up to my FPGA dev board? I was thinking I could get a very small conductive wire, and place it through the test-points which are on all the traces leaving the chip, and solder the fine wire to my larger-wire(which goes to the breadboard and eventually the one of the User FPGA I\O pins). How would I keep this neat and stop a short-circuit with such dense pins? Are there specialized wires for this or something? Will this disrupt the signal at all though provided I am just logging all the relevent pins on the ROM? And can I trust the XBox will access all of this memory? Because if it doesn't I won't get a full dump of the ROM chip.

Edited by Jeremy_, 20 August 2010 - 01:17 PM.


#2 obcd

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Posted 26 August 2010 - 01:57 PM

What is your purpose of this setup?
Soldering additional wires to the fast changing adress and data lines of the flash rom chip might change the capacitance of those signals. It's hard to tell if things will still work as expected with that extra load.
It's possible to use the phoenix bios loader to load another kernel from the harddisk.
That's probably why the author says that the original kernel resides in the flash rom.

regards.


#3 Bomb Bloke

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Posted 27 August 2010 - 02:30 AM

QUOTE(Jeremy_ @ Aug 20 2010, 08:09 PM) View Post
My first question is, the author of a book I'm reading says the 'initial' kernel is stored in this ROM chip. My question is what does he mean when he uses the word initial? Is there more than one kernel?

You're talking about the one stored in the TSOP, yes? When the console boots, it copies that to RAM, then uses that new copy for the duration of the session. This is what makes softmods possible - they can't alter the version stored in the TSOP itself, so instead they mess with the one in RAM (which is actually being used anyways).

Though for some reason, the TSOP gets checked again every time a new XBE gets launched. Not sure why. But while just idling (or playing a game or something), that chip will be left alone by the system.




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