Breadboarding A 4-bit ALU

September 10, 2012 by Mike Szczys 8 Comments

[TGTTGIT] recently took the plunge and decided to build his own computer using logic chips. He just completed a 4-bit ALU which can compute 18 functions. It took a long time to get the wiring right, but in true geek fashion his build was accompanied by an alternating Chapelle’s Show and Star Trek: TNG marathon playing in the background.

This project is the stepping stone for a larger 16-bit version. The experience of wiring up just this much of it has convinced him that an FPGA is the only way to go for the future of the build. But since he had already ordered the chips it was decided that the only thing to do was to see this much through. He used the truth table from The Elements of Computing Systems for the design and posted several times about the project before arriving at this stopping point so you may be interested in clicking through the other post on his blog. There’s also a lot of other TTL computer projects around here worth checking into.

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Computer Desk… Literally

June 30, 2012 by Mike Szczys 28 Comments

This piece of furniture begs the question, why think of a desk and a computer case as separate things? It combines Ikea furniture with electronic hardware to create the ultimate command center.

First the obvious parts: there’s a nook for the computer case that hangs just below the desktop off to the side, and the twin displays are mounted front and center. The divider between the cabinet pieces was cut away to allow the monitors to be wall-mounted. But things start to get interesting to the left of those monitors. You can see a series of dial displays in the door for that cabinet. Those meters were sourced from the MIT Flea Market and after a bit of alteration they display CPU load information fed to them by an Arduino board. This also drives some LED strips which are mounted behind the frosted glass panel that we guess could be called a back splash. The heavier the load, the better the light show.

All of the power management is taken care of in the cabinet to the right of the monitors. The top row hides a printer, external hard drive backup system, and several gaming consoles. Heat will be an issue so exhaust fans were added to each of these partitions. They’re switched based on a temperature sensor in each. It’s a lot of work, but the outcome proves it was worth it.

[via Reddit]

Calculating With 3D Printed Gears

June 11, 2012 by Brian Benchoff 5 Comments

Here’s a 3D printed electromechanical computer built by [Chris Fenton] over at NYCResistor. It uses plastic registers printed on a Makerbot, a bunch of pogo pins, and business-card sized punch cards capable of storing 32 bits of instructions and data.

In case you’re wondering, this isn’t the first time we’ve seen [Chris]’ FIBIAC. Since the last update, [Chris] managed to get a program that walks through the first three digits of the Fibonacci sequence. There’s really no limit to what the FIBIAC can theoretically do, but with only three registers he’s limited to calculating the first three digits of pi.

With more registers, [Chris]’ computer could be expanded, but each register takes about 8 hours to print. We’re sure [Chris] would gladly accept any donations of additional 3D-printed registers, so if you’d like to make a few of these gear registers you can get the files on Thingiverse.

As a proof of concept, [Chris]’ FIBIAC is amazing, but it doesn’t live up to its intended design. The punch card format [Chris] created is capable of storing 8 registers, and the registers themselves can be expanded far beyond their current 3-digit width. Still, it’s an incredible build and has the bonus of being easily expandable thanks to a very clever design.

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Build An 8-bit TTL Computer

May 7, 2012 by Brian Benchoff 10 Comments

Very rarely do we see an Instructable so complete, and so informative, that it’s a paragon of tutorials that all Instructables should aspire to. [8 Bit Spaghetti]’s How to Build an 8-bit computer is one of those tutorials.

[8 Bit Spaghetti]’s build began on his blog. He originally planned to build a 4-bit computer but decided a computer that could only count to 15 would be too limiting. The build continued by programming an NVRAM as the ROM on a breadboard and finally testing his bundle of wires.

What really makes [8 Bit Spaghetti]’s special is the Instructable – he covers just about all the background information like the definition of a Turing machine, a brief introduction to electronics and logic chips, and binary numbers. Even though he’s doing some fairly complicated work, [8 Bit Spaghetti]’s tutorial makes everything very clear.

The computer isn’t quite done yet – there’s still a few nixie tubes to add – but we couldn’t imagine a better project for the budding electronic hacker.

8-bit Computer Project Lands In A Philco Radio Case

March 5, 2012 by Mike Szczys 17 Comments

We’ve enjoyed seeing the development progress of Veronica, [Quinn Dunki’s] 8-bit computer project. It started out on a breadboard, then moved to edge-connected PCBs, and now [Quinn] has given Veronica a body of her own.

The donor is a Philco Model 42-327T and was produced in 1942. It was chosen because it is non-functional and missing several pieces. We wonder about the collector’s value of the piece but since [Quinn] snagged it from eBay there can’t be in huge demand right now. The teardown images are priceless. There seems to be no reasoning behind component placement for the beast. It looks more like a junk drawer packed full of relic components than something that actually worked once upon a time.

But we digress. After gutting the retro wooden case [Quinn] set out to fabricate her own face plate. Since she’s comfortable working with copper clad, she whipped up a negative design and etched the dashboard seen above. It mounts in the original dial opening, and hosts all of the controls she needs to work with the 8-bit computer. Just below is where the present buttons used to be located. You can just see the hexout display for reading data from the registers mounted in that void.

The TIM-8 Is The Smallest 8-bit Relay Computer Ever

January 16, 2012 by Brian Benchoff 20 Comments

Who wouldn’t want to build a computer out of relays? We do, but we’ve got too many projects on our plate already. It looks like [rory] has his priorities in order because his build is one of the most amazing we’ve ever seen.

We’ve seen [Harry Porter]’s amazing relay computer and we’re familiar with [Konrad Zuse]’s WWII era endeavours. Relay computers aren’t exactly uncommon, but [rory] built the TIM-8, that may be the smallest 8-bit relay computer ever. The total relay count in the TIM-8 is 152 compared to [Harry Porter]’s 415 relays. This isn’t a fair comparison because [Harry]’s uses 4-pole relays, while the TIM-8 uses 1-pole relays, making the [rory]’s project 8 times smaller than [Harry]’s.

There are a couple of neat features that makes the TIM-8 really exceptional. Programs for the TIM-8 are written in a text editor on [rory]’s desktop, then compiled and printed onto receipt paper. The TIM-8 has a few phototransistors to read the bands of white and black printed on the paper. [rory] has come a long way from a three bit adder made with relays and light bulbs.

Check out a ton of videos after the break. There’s a few demos of programs running off of receipt tape, calculating the Fibonacci sequence, and playing ‘Mary Had a Little Lamb’ on the relay sound card. Thanks to [J. Peterson] for sending this one in.

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Programming The 6502 One Nibble At A Time

December 7, 2011 by Mike Szczys 36 Comments

[Quinn Dunki] keeps rolling with her 6502 based computer build. This time around she’s added some memory to store the programs, but needed a way to get that code into the device. Above is her solution, a bank of hex switches used to program the 8-bit command and 16-bit address for each line of machine code.

This is a continuation of her Veronica project. The last time we saw it she had hardwired the logic levels for the data bus, but that’s no fun since nothing can actually be computed. [Quinn] picked up an SRAM chip which will store the program. It’s compatible with the 6502’s memory bus, but needs a bit of extra circuitry for her to be able to hand program it with this switch bank. She used some tri-state buffers to switch between connections to the processor, and to the hex switches. This way, she disconnects the RAM from the processor using the buffers, uses the switches and push button to clock in the program, then patches the RAM back into the computer.

Seeing this process in the video after the break certainly gives you an appreciation for what an improvement the punch-card system was over this technique. Still, seeing this is a delight that we’d like to try! Continue reading “Programming The 6502 One Nibble At A Time” →