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## 4xxx logic computer

Started by Vijfhoek, September 30, 2015, 12:42:06 AM

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#### Vijfhoek

Hey, it's been a while since I've been active here, which is really something I should do something about. So how about posting this project I've been working on lately here? Sounds like a plan!

Recently I got a bunch of wires, breadboards and logic ICs (4070 (xor), 4071 (or), 4081 (and) and 4539 (4-input mux) to be precise), with which I'm planning on making a (probably) 8-bit computer. Currently, I'm working on figuring out how to most efficiently make it - breadboards are really quick but a cluster**** of wires, perfboards are pretty neat but cost lots of time to make, and I suck at designing PCBs and they are a hassle to make.

I already have a working 2-bit ALU (arithmetic logic unit, the calculaty part of a processor) on a breadboard, which can be expanded easily, and I'm working on making the same 2-bit ALU on a perfboard, to see how that turns out. I should be able to connect those two versions together to get a messy 4-bit ALU, I suppose. I'll see!

The ALU I'm working with currently has the ability to invert either of the inputs, a carry in/out and three functions (AND, OR and ADD) which can be combined to do lots of stuff. For example, to subtract, carry in has to be enabled and input B has to be inverted.

Anyway, I currently don't have any nice non-shaky pictures or videos to show, I'll take a few of those with some precious daylight tomorrow.

#### novenary

#1
Sounds like fun, good luck !

Quote from: Vijfhoek on September 30, 2015, 12:42:06 AM
I suck at designing PCBs and they are a hassle to make.
PCBs are only for final designs, for prototyping sticking to bread/perf boards is a good idea. That aside I found designing a board to be fairly simple when you know what kind of circuit you're making (always use the schematic tool of your CAD application, it helps a lot). Homebrew PCBs indeed look like a pain to make, I again would only do that to test a design before sending it out to a professional fab like OSH Park which is cheap and you get quality boards. Then there's assembly, you're probably going to stick to through hole components though you can mix through hole chips and SMD passives to save board space. Through hole is slightly easier because alignment is not a concern, I myself when straight to full SMD after having only experience soldering wires, watched a few videos on the subject and the result is very satisfying.

Left and right are blank copies of the fully assembled board in the middle, SD card for scale. The blob thing between the two chips in the middle-top is just flux that I can't clean because I don't have the products to do so.

#### Dream of Omnimaga

I sadly never heard about 4xxx stuff before, but I am curious about what you'll come up with. Keoni29 used to make 8-bit computers before, most being 6502 and Z80, but he is no longer interested in CW it seems. I wish you good luck Vijfhoek.
• Calculators owned: TI-82 Advanced Edition Python TI-84+ TI-84+CSE TI-84+CE TI-84+CEP TI-86 TI-89T cfx-9940GT fx-7400G+ fx 1.0+ fx-9750G+ fx-9860G fx-CG10 HP 49g+ HP 39g+ HP 39gs (bricked) HP 39gII HP Prime G1 HP Prime G2 Sharp EL-9600C
• Consoles, mobile devices and vintage computers owned: Huawei P30 Lite, Moto G 5G, Nintendo 64 (broken), Playstation, Wii U

#### p4nix

Is keoni active somewhere else, or is he entirely lost? :c
• Calculators owned: fx9860GII (SH4)

#### novenary

#4
We chat with him pretty often on Telegram, otherwise he's nowhere to be seen.

Quote from: DJ Omnimaga on October 03, 2015, 08:45:04 PM