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Building an 8-bit Computer: Part 1 - Procurement

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Intro

Welcome to the first blog post in my Building an 8-bit Computer series. In these posts, I will be documenting my journey of learning the fundamentals of computing through building Ben Eater's 8-bit computer from scratch. This blog is a work in progress and mainly for retrospection on the interesting things I learn along the way.

In this post, I will be going through why I decided to build an 8-bit computer and the procurement of components required to get started.

What is Ben Eater's 8-bit computer?

Ben Eater's 8-bit computer is a video series documenting Ben Eater project to build a computer built from scratch on breadboards using only simple logic gates.

https://eater.net/8bit/

If you are thinking of doing this yourself, Ben Eater seems to have a cult following on Reddit (which hopefully I will be part of soon). I would recommend checking out this community here: r/beneater

Why?

I've been interested in electronics and computers from a young age, having recently started a career as a software developer in Ruby and JavaScript stacks, both high-level langagues. However, since learning the basics of how a CPU works in the Introduction to Computing module in my Mechanical Engineering degree, I have been curious about how computers work from the ground up.

Having no experience in low-level languages, I know there is a significant gap in my understanding of computer programming. Learning computing at a lower level would improve my knowledge of the languages I work in and possibly open up new opportunities for hobbies and work.

I have a basic understanding of electronics, such as the physics of circuits and how semiconductors and gates work. But any further than that, it's a black hole.

I discovered Ben Eater through YouTube recommending his excellent video on binarary adition using logic gates, it piqued my interest, and I started exploring his channel and website. From there, I saw the 8-bit computer project and thought I might as well jump in at the deep end and force myself to get the deeper understanding I need. It's also fun learning a new technology field, particularly one where it provides the potential to create almost anything.

I intend to research and understand how each component works throughout the project, so it'll probably take a lot longer than I'd expect if it was just plugging components. I'll keep note of how long it takes and let you know in the conclusion post.

Procurement

Since I live in the UK, I decided not to buy the package Ben Eater sells on his site due to import tax and shipping, so I went about going through the parts list and buying chips.

It took about 4 hours to purchase all of the components, some of which seemed hard/impossible to get locally in the UK. Regarding chip numbers, commonly, I found the correct part number but with suffixes such as an N after it. I'm not sure if this means anything yet. I briefly read the datasheets (which, after watching a couple of videos, seem very important), and I am confident I will be able to wire it up correctly if I understand the logic of the chip does and its spec. However, I'll likely look back on this statement and cringe at how wrong I was 😅

Computer Parts

Qty Component Seller Price (£)
3 SN74LS00N RS Components 1.73
6 SN74LS04N RS Components 3.96
4 SN74LS08N RS Components 2.35
2 SN74LS32N RS Components 1.10
3 SN74LS86AN RS Components 1.73
1 SN74LS74AN RS Components 0.58
1 SN74LS139N RS Components 0.76
5 SN74LS151N RS Components 4.14
7 SN74LS245N RS Components 5.63
5 SN74HC595N RS Components 2.76
2 SN74LS273N RS Components 1.56
1 8-way DIL switch RS Components 1.51
1 DIP switch SPST RS Components 1.22
50 Red LED 5mm RS Components 14.88
20 Green LED 5mm RS Components 3.70
10 Yellow LED 5mm RS Components 2.42
25 Blue LED 5mm RS Components 10.32
1 SN74LS107AN Farnell 2.14
1 SN74LS138N Farnell 0.9
10 SN74LS173AN Farnell 13.08
2 SN74LS283N Farnell 3.43
3 SPDT Slide Switch Farnell 4.36
10 SPNO Switch Farnell 0.84
4 Seven Segment Display Farnell 4.34
2 USB 2.0 2m cable Amazon 4.29
1 5A USB plug adapter Amazon 7.64
1 74F189 64-Bit RAM eBay 5.99
1 SN74LS139N eBay 1.95
1 SN74LS161AN eBay 3.00
3 16K CMOS Parallel EEPROM eBay 19.11
8 SN74LS86N eBay 5.00
10 2 Pin PCB terminal block eBay 2.49
3 3 pin SPDT Slide Switch eBay 2.05
100 22awg Hook up Wire eBay 17.25
15 K&H RH-21 840 Breadboard Rapid 126.36
100 1K 0.5W Resistor Rapid 1.56
100 10K 0.25W Resistor Rapid 1.05
100 100K 0.25W Resistor Rapid 1.05
100 470R 0.25W Resistor Rapid 1.05
100 1M 0.25W Resistor Rapid 1.05
1 Finger Adjust Pot Rapid 0.94
5 10nf Capacitor Rapid 0.63
25 100n Capacitor Rapid 2.46
5 1uF Capacitor Rapid 2.87
5 NE555P Rapid 2.36
5 SN74HC02N Rapid 1.53
5 CD74HCT73E Rapid 3.63

Tools

Qty Component Seller Price (£)
1 Wera PH0 screwdriver Rapid 3.01
1 Wera PH1 screwdriver Rapid 3.48
1 Wera 0.18 Slotted Screwdriver Rapid 3.23
1 Bugari Needle Pliers Rapid 13.79
1 Bugari Blade Cutters Rapid 13.09
1 Anvil Wire Stripper Rapid 5.29
1 Arduino Nano Evaluation Board Farnell 17.28
1 AN8008 Digital Multimeter Amazon 24.05
1 120pc Jumper Wire Cable Set Amazon 3.49

As you can see when comparing to the required list of components, many companies had minimum purchase quantities, which was a downside to ordering them myself. The upside is that this does give some redundancy for broken components and supplies any future projects.

The full stash of components and tools
The full stash of components and tools

Total for components came to £304.73
Total for tools came to £86.71

For a very basic computer, this might seem like a lot of money. I did get a couple of comments from the missus asking me what more it could do than a £5 calculator while costing the same amount as a low-end laptop. To that, the only answer I have at the time is "it's a hobby" and "it might teach me C". Hopefully, I'll learn a lot and have some fun.

What's Next

The project's next step is to build the first part of the computer, the clock module.

Check back later to see this post.