What is Reddit's opinion of Digital Computer Electronics?

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If you prefer to read this as a book, the computer is based on the SAP computers (Simple As Possible) in Albert Malvino's book Digital Computer Electronics. The book goes on to describe slightly more complex architectures as well.

Just a heads up for anyone that doesn't care to watch videos, I believe this design is based on the SAP1 (Simple As Possible) computer design, one of the three designs described in the book Digital Computer Electronics by Albert Malvino. We used that book in high school and it's really good at explaining how computers work. I remember building a simulator for the SAP1 and SAP2 at that time, and it was great fun.

here’s an amazon link to the book i got (Digital Computer Electronics https://www.amazon.com/dp/0028005945/ref=cm_sw_r_cp_apip_yHyYsN4bBKFqR). It honestly serves as a near perfect guide to all this. There are some things that he doesn’t have though, like making the 3 Digit Display for output and some additions in the clock module. For understanding a basic CPU tho, you couldn’t ask for a better book.

Currently trying to read through all of the Discworld series, the reading part is easy, but obtaining all 42 books is the hard part :P

Also Digital Computer Electronics by Albert.P.Malvino, which may look like it is complicated, but is really more like an old Computing For Dummies that I'm reading since my country's curriculum doesn't actually teach anything except the basics of electronics and computing :(

I work with a group of 8th graders who spend last term building this 8-bit computer from scratch.

None of them had ever been close to the metal before - and since it's all on solderless breadboards there were no issues with the parents or admins who get uptight about soldering projects. I plan on using it often - the textbook this project is based on is still in print and on Amazon.

Ok let's see if I can explain.

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First it helps to know that the 74LS173 has a built-in 50 ohm resistor on each output. Remember that in a second below.

Diodes and transitiors are not "ohmic" devices -- they don't obey Ohm's law like a resistor does. Diodes in particular have a built-in voltage-drop that applies when you hook them up in the forward direction. That is the "forward-bias". It's different for each diode but it was 1.5V on my LEDs. Basically the diode is either 0V for off or 1.5V for on.

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When combined with the built-in resistor (Ri) inside the 74LS173, this creates a voltage divider circuit: 5V-----Ri-----pin----LED----0V

The diode "takes" 1.5V of the 5V and Ri gets the other 3.5V. This way your diode doesn't burn up, but if you measure the voltage *at the pin* you will see it's only 1.5V for a 1! That's too low and the 74LS245 sees a 0 at its input.

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Now if you add a resistor of your own, say 470, it changes the voltage divider circuit into a 3 stage: 5V-----Ri-----pin----R470-----LED----0V

The diode still "takes" 1.5V, leaving 3.5V shared between the 2 resistors. This is a 2-stage divider. Of that 3.5V, Ri will take only 0.3V and R470 will take the other 3.2V, based on Kirchoff's Voltage law. Now the voltage *at the pin* is 4.7V for a 1, which works great!

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Recommendations for general electronics...definitely https://artofelectronics.net/

Ben's computer is basically the SAP-1 from this book: https://www.amazon.com/Digital-Computer-Electronics-Albert-Malvino/dp/0028005945

It's an amazing book. Something else you might enjoy,

Ben Eater"s Build an 8-bit computer from scratch

If you actually get the kits to make the computer, make sure you read these:

What I Have Learned: A Master List Of What To Do

Helpful Tips and Recommendations for Ben Eater's 8-Bit Computer Project

As nobody can figure out how Ben's computer actually works reliably without resistors in series on the LEDs among other things!)

He mentions a book he used at the beginning of his series. I think it is this, https://www.amazon.com/Digital-Computer-Electronics-Albert-Malvino/dp/0028005945

https://www.amazon.com/Digital-Computer-Electronics-Albert-Malvino/dp/0028005945

This out of print book is soooo good. I recently took an FPGA class and pulled this off my shelf for review after several minutes of frustrated googling

/r/pcmasterrace has guides on how to build computers at different price points. In fact I think they have a $400 example computer.

Any cheap old edition of this book will help teach you how they work on the inside https://www.amazon.com/Digital-Computer-Electronics-Albert-Malvino/dp/0028005945

As will this http://www.nand2tetris.org/

And if want to learn how to code this is a common recommendation https://learnpythonthehardway.org/

OK, I'm late to the party on this, and you seem to have settled on the FPGA route. I too was interested in building my own a few months ago but I came to a very different conclusion. The book that kept popping up was Digital Computer Electronics by Albert Malvino. It's 20 years old but much of the concepts and theory still form the basis of modern processor design. The book starts with how a logic gate actually works at the transistor junction level and then builds up to the 8085/6502 CPUs. Included in the book is a complete schematic for a primitive discrete logic computer call the SAP-1 Simple As Possible Computer.

I have built one virtually using a circuit simulation program and also did some updates to the design to use modern components. My schematics are available in this post.

Over in /r/cpudesign another redditor made his own SAP-1 on a breadboard and outlined his work on the website http://8bitspaghetti.com/