

Reverse-engineering the flag circuits in the 8085 processor - kogir
http://www.righto.com/2013/07/reverse-engineering-flag-circuits-in.html?m=1

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kogir
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.

~~~
fein
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.

~~~
kens
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.

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kostyakow
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](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!

