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Ah, you are correct, I got confused watching some video of someone hacking away at the built in ROM on a de-caped chip... suffice to say, overwriting the perman
by tomxor 9y ago
Ah, you are correct, I got confused watching some video of someone hacking away at the built in ROM on a de-caped chip... suffice to say, overwriting the permanent internal copy of the microcode does not normally happen. The advantage of updating the ROM this crazy way is purely to defeat the verification of the signature.
- bayindirh 9y agoCare to share the URL of the video? It sounds pretty fun.
- tomxor 9y agoIt was a hacker news post actually: the presenter's delivery is a bit dry... but his project is impressive: https://media.ccc.de/v/34c3-9058-everything_you_want_to_know_about_x86_microcode_but_might_have_been_afraid_to_ask#t=2467 https://media.ccc.de/v/34c3-9058-everything_you_want_to_know... The SEM shots of the internal RAM/ROM starts around 24:00, I thought it was pretty cool. The whole purpose of what they are doing is to try and reverse engineer the microcode to write their own.
- bayindirh 9y agoThanks, I'll take a look tomorrow. For more uCode work, there's http://inertiawar.com/microcode/ http://inertiawar.com/microcode/ which contains some interesting bits.
- tomxor 9y agoThanks, I do find microarchitecture stuff really interesting but it's a bit out of my depth if i'm honest.
- bayindirh 9y agoI find CPUs fascinating to be honest. While they are complex, they are not impenetrable. Playing with small assembly snippets and simulators helped me a lot to understand them. Also, other architectures such as MIPS and M68K have simpler to understand ISAs which accelerate the process of understanding these small wonders.