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Reverse-engineering the flag circuits in the 8085 processor (righto.com)
64 points by kogir on July 18, 2013 | hide | past | favorite | 4 comments



I find stuff like this fascinating and marvel at how it's even possible to do via visual inspection alone.

It's also sobering to think about how long it would take using a similar process to understand a modern, 20 nanometer chip.


I always look at things like this and say that I wish I understood every step of the process, from electrical theory to fabrication.

I have the same approach to software, but I have to keep reminding myself that the things I'm trying to understand took hundreds of people to complete. It's an incredibly annoying internal struggle. I have no idea how to deal with it aside from grinding it all out until I die.


Author here: I don't understand every step of the process either :-) But old chips like this at least seem theoretically possible to comprehend in their entirety. I expect it would be pretty much impossible to reverse-engineer and understand a present-day processor with billions of transistors instead of thousands. But I could be surprised - 35 years from now people may be reverse-engineering Xeon chips for fun. And perhaps posting about interesting things they found in Intel's random number circuitry.


Thank you for this this great article!

I am currently trying to learn more about the hardware and lower-level aspects of computer, and this was a really interesting read.

You may be interested in checking out an emulator for original IBM computer my friend wrote:

https://github.com/Alegend45/IBM5150

It's in really early stages of development, and the BIOS barely boots. Nevertheless, I enjoy reading the code and trying to understand how it works.

I am trying to help him out with it, but I know very little about this kind of stuff (I am just starting out learning about hardware), so I haven't been of much help.

Since you are knowledgeable in this subject area you can help him hack on it if you're interested!




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