ALU Design

In this video we go over the design for the Arithmetic and Logic Unit for our 8-bit computer.

Before watching it's helpful to understand:

[DingleTwit]

I really love the hand drawn diagrams and the pull-the-paper-away reveals. No dumb animations that are all flash without actually enhancing the knowledge being shared.

[giantneuralnetwork]

That was awesome when the carry in on the first adder swooped in like a hero at the end to bring us to two's complement! Really enjoying these, thanks for your time and effort!

[snork_games]

13:30 that carry in solution blew my mind

[hansklaus]

lol even before he showed how to invert the signal, I was already like "oh, and for adding one he can just use the carry thing on the 4 bit adder"
so then he says "it just so happens that our 4 bit adder..."
me: "do it! do it!"
him: "...has a carry in"
he draws the line
me: "oh my god! oh my god! he did it, he drew the line! I feel so smart right now!"

I never thought i'd ever be this excited about a line...

[johnwilson]

Ben, I would just like to thank you for taking the time to make these videos. They are brilliant! Thank you.

[cesarjesusvalls]

I am still amazed by this series of videos. This is simply magnificent. I do not even know how to explain how much I appreciate your tutorials. Thank you so much for this open gift to all people who looks for understand how a computer works from scratch. As a PhD student in particle physics who never found college instructive I can honestly say this is how things must be taught in any branch of knowledge. Thanks again!!!

[danielstephenson]

What I really enjoy about these videos is Ben will introduce a system or premise but not overwhelm you with everything in one go, but rather reveal things as they're necessary. Loving these videos and really appreciate the preparation you go through in order to make it as clear as possible!

[prateekmahajan]

"The different between 1's complement and 2's complement is 1", Awesome

[mikhailglukhov]

Fantastically beautiful design!

I am a software developer, and these days maybe only 1% of developers know how the processor is working on the very low level of registers, logic gates and transistors. We just write high level code and have no idea how it is processed 😅

[willofirony]

I think I have watched this video over 5 times; not because I am having difficulty understanding it, this IS a Ben Eater video after all. No, it is because I just love the carry in twist. Pure paracetamol.

[aaronfuzion]

The implementation came together so elegantly with the xor inversions and the carry in adjustment. Blew my mind!

[colebot]

I love that I could easily build all of this solely from logic gates or even just transistors with these videos

[serayamartinez]

You're the best tutor I've had! I went through five tutors a while back: two of which were through a professional tutoring agency and zero of which were provided by my school because they didn't have any. In all cases the reason for lack of qualified tutors was because no one understood any of this. I needed to understand this stuff for programming classes I was taking. Thank you!! And, finally!!

[CodeWithSen]

I recommend reading the book 'But How Do it Know', it's a great book about computer architecture and even though I am a software developer, and not a computer engineer, it still helped me to understand a ton about computer languages, especially assembly.

[TheSgrizli]

Definitely better than my university course as always. Idk why YT videos have became better learning platforms than most schools. Don't go to uni guys you can learn everything online

[chitlitlah]

I was wondering why, when programming for the 6502, you generally _clear_ the carry bit before adding but _set_ the carry bit before subtracting. Not anymore. This is brilliant.

[shmarvdogg]

i dont have components to play with but i found this piece of software that allows you to design and simulate circuits with logic gates and i made a 8 bit addition and subtraction circuit and when i got it to work it was the most amazing thing ever. This is without a doubt the most fun part of computers.

[ncank]

watching this series again after 7 years and it's still unbeatable.

[MAgyko]

Unbelievable simplicity of explanation, I wish I know about you 5 years ago.
Well done Ben 👏

[S-MKim]

the architecture of the 2s compliment adder is very simple and beautiful. congraturations to the lucky person who made this first.