Homebrew RISC-V Computer Has Beauty And Brains

Building your own CPU is arguably the best way to truly wrap your head around how all those ones and zeros get flung around inside of a computer, but as you can probably imagine even a relatively simple processor takes an incredible amount of time and patience to put together. Plus, more often than not you’re then left with a maze of wires and perfboards that takes up half your desk and doesn’t do a whole lot more than blink some LEDs.

An early prototype of the Pineapple ONE.

But the Pineapple ONE, built by [Filip Szkandera] isn’t your average homebrew computer. Oh sure, it still took two years for him to design, debug, and assemble, his 32-bit RISC-V CPU and all its associated hardware; but the end result is a gorgeous looking machine that runs C programs and offers a basic interactive shell over VGA. In fact with its slick 3D printed enclosure, vertically stacked construction, and modular peripheral connections, it looks more like some kind of high-tech scientific instrument than a computer; homebrew or otherwise.

[Filip] says he was inspired to build this 500 kHz (yes, kilohertz) beauty using only discrete logic components by [Ben Eater]’s well known 8-bit  breadboard computer and [Robert Baruch]’s LMARV-1 (Learn Me A RISC-V, version 1). He spent six months simulating the machine before he even started creating the schematics, let alone design the individual boards. He tried to keep all of his PCB’s under 100 x 100 mm to take advantage of discounts from the fabricator, which ultimately led to the decision to align the nine boards vertically and connect them together with pin headers.

In the video below you can see [Filip] start up the computer, call up a bit of system information, and even play a rudimentary game of snake before peeking and poking some of the machine’s 512 kB of RAM. It sounds like there’s still some work to be done and bugs to squash, but we’ve already seen enough to say this machine has more than earned entry into the pantheon of master-crafted homebrew computers.

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Homebrew 68K Micro-ATX Computer Runs Its Own OS

We’re no stranger to home built Motorola 68000 computers here at Hackaday, but more often than not, they tend to be an experiment in retro minimalism. The venerable processor is usually joined by only a handful of components, and there’s an excellent chance they’ll have taken up residence on a piece of perfboard. Then [NotArtyom] sent in his Blitz, and launched the bar into the stratosphere.

Make no mistake, the Blitz isn’t just some simple demo of classic chips. The open hardware motherboard has onboard floppy, IDE, and PS/2 interfaces, with a trio of 8-bit ISA expansion slots for good measure. The  Motorola 68030 CPU is humming along at 50 MHz, with 4 MB of RAM and 512 KB of ROM along for the ride. Designed to fit the Micro-ATX motherboard standard, you can even mount the Blitz in a contemporary PC case and run it on a standard ATX power supply.

An earlier prototype of the Blitz motherboard.

As if the hardware wasn’t impressive enough, [NotArtyom] went ahead and created his own open source DOS-like operating system for it to run. Written in portable C, G-DOS can run on various m68k boards as well as ARM and PowerPC machines. It’s an incredible project in its own right. If you’re looking for something to show off your homebrew computer, you could certainly do worse than pulling down a copy of G-DOS. If you do port it to a new board, make sure to let [NotArtyom] know.

It’s taken [NotArtyom] three years to develop Blitz and G-DOS with his only goal being to better understand homebrew computers. He has no interest in monetizing the design or turning it into a kit, but instead hopes it will be a resource and inspiration for others with similar interests. Oh yeah, and he did all of this before he even graduated high school. If you weren’t questioning your life’s accomplishments before, now would be a great time to start.

Interested in building your own Motorola 68000 computer, but haven’t yet attained the wizarding level of [NotArtyom]? You could start with something a bit simpler like the 68k-nano, or if you’re really in a pinch, just dead bug a Dragonball 68328.

Four Chips To Retro Perfection

Over the years, we’ve seen many people build a computer from the ground up. It’s always great, but this one takes the cake. I’m not just saying that because there’s a cute little ‘Z80 Inside’ logo on the silk screen, either. It’s a four IC Z80 computer, a tiny board, and [Just4Fun]’s entry into this year’s Hackaday Prize.

This single board computer is only four chips, the most important being the CMOS Z80 CPU. This is the same CPU as was found in the TRS-80 and the ZX Spectrum, both classics from the early days of computing. In addition to the PCU, there’s a Toshiba SRAM with 128 whole kilobytes of random access memories. A 74HC00 is thrown into the mix for glue logic, and everything else happens through a specially-programmed ATMega32A. This last chip provides a universal I/O subsystem, the EEPROM, and the 4/8MHz clock for the CPU.

Those four chips are really all you need for a fully functional computer, but you can do so much more with this little board. There’s a uCom board, or basically a ‘transparent’ USB-to-serial emulator that will allow you to upload a hex file to the board. Of course this means you can also connect it to a terminal, and with FuzixOS, there’s Unix for the Z80. It’s a wonderment of retrocomputing, and one of the best ways to build an old computer today.

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A Nearly Practical 6502 Breadboard Computer

Over the years we’ve seen a number of homebrew 6502 computers assembled with little more than a breadboard, a sack full of jumper wires, and an otherworldly patience that would make a Buddhist Monk jealous. Anyone who takes the time to assemble a fully functional computer on a half-dozen breadboards lined up on their workbench will always be a superstar in our book.

While we’re still too lazy to attempt one of these builds ourselves, we have to admit that the Vectron 64 by [Nick Bild] looks dangerously close to something you might be able to pull off within a reasonable amount of time. It’s still an incredible amount of work, but compared to some of the other projects we’ve seen, this one manages to keep the part count relatively low thanks to the use of a simple 16×2 LCD for output and user input provided by a PS/2 keyboard. You won’t be playing Prince of Persia on it, but at least you might be able to finish it in a weekend.

The computer is clocked at 1 MHz, and features 32KB RAM
along with 32KB EEPROM. That should be enough for anyone. [Nick] also points out he tried to use era-appropriate 7400 series ICs wherever possible, so no worries about historical revisionism here. If you’re looking for a design that somebody could have potentially knocked together back in the 1970s, this one would get you fairly close.

The astute reader might notice there’s no removable media in this build, and may be wondering how one loads programs. For that, [Nick] allowed himself a bit of modern convenience and came up with a scheme that allows an Arduino (or similar microcontroller) to connect up to the computer’s 28C256-15 EEPROM. With a Python script running on your “real” computer, you can write a new ROM image directly to the chip. He’s included the source code for a simple program which will write whatever you type on the keyboard out on the LCD, which should give you a good framework for writing additional software.

If you’re looking for a bigger challenge, don’t worry. We’ve covered 6502 breadboard computers that will make your eyes water. Incidentally, this isn’t the first time we’ve seen a similar LCD used for one of these computers, so looks like there’s no shame in sneaking in modern parts where it makes sense.

VCF West: Homebrew Lisp Machines And Injection Molded PDPs

Someone walks into the Vintage Computer Festival and asks, ‘what’s new?’. It’s a hilarious joke, but there is some truth to it. At this year’s Vintage Computer Festival West, the exhibit hall wasn’t just filled to the brim with ancient computers from the Before Time. There was new hardware. There was hardware that would give your Apple IIgs even more memory. There was new hardware that perfectly emulated 40-year-old functionality. There’s always something new at the Vintage Computer Festival.

Some of the more interesting projects are just coming off the assembly line. If you want a modern-day Lisp machine, that one won’t be assembled until next week, although there was a working prototype at VCF. If you want the greatest recreation of the most beautiful hardware, VCF has your back. Check out these amazing builds below.

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Another 74XX Series CPU

[Jack Eisenmann] is no stranger to building impressive DIY CPU’s on vast stretches of breadboard. This time [Jack] has done away with the seventeen breadboards he used in his last 8-bit computer and instead has gone a step further and designed a set of generously utilised PCB’s for the CPU. The result is the DUO Enterprise.

The CPU design is based around an 8-bit data bus and a 24-bit address bus. As usual, a minimal yet carefully chosen instruction set allows [Jack] to do all the heavy lifting in software as part of the compiler and operating system he is working on. There is no sign of a display yet, instead the computer communicates via a dumb terminal. We love the aluminum foil for shielding! Check out the video, below, to see what we mean.

Over the years, we have seen many of [Jack]’s other CPU builds featured on Hackaday. One of his first designs was a 4-bit CPU that could play many games on a LED matrix.Later he did a much more impressive 8-bit CPU along with analog video output and an OS ofcourse. It could even play pong. He even built a Single Instruction Set Computer (SISC).

His final goal with DUO Enterprise is to allow anyone to utilise its computing power by submitting programs and calculations. Heads up [Jack], our neural net needs training soon.

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The Cardboard Computer

Every time we say “We’ve seen it all”, along comes a project that knocks us off. 60 year old [Mark Nesselhaus] likes to learn new things and he’s never worked with hardware at the gate level. So he’s building himself a 4-bit Computer, using only Diode-Transistor Logic. He’s assembling the whole thing on “card board” perf-board, with brass tacks for pads. Why — because he’s a thrifty guy who wants to use what he has lying around. Obviously, he’s got an endless supply of cardboard, tacks and Patience. The story sounds familiar. It started out as a simple 4-bit full adder project and then things got out of hand. You know he’s old school when he calls his multimeter an “analog VOM”!

It’s still work in progress, but he’s made a lot of it in the past year. [Mark] started off by emulating the 4-bit full adder featured on Simon Inns’ Waiting for Friday blog. This is the ALU around which the rest of his project is built. With the ALU done, he decided to keep going and next built a 4-to-16 line decoder — check out the thumbnail image to see the rats nest of jumbled wires. Next on his list were several flip flops — R-S, J-K and D types, which would be useful as program counters. This is when he bumped into problems with signal levels, timing and triggering. He decided to allow himself the luxury of adding one IC to his build — a 555 based clock generator. But he still needed some pulse shaping circuitry to make it work consistently.

from right, Input, +5V, nc, gnd
LED Driver : from left, Gnd, NC, +5V, Input

[Mark] also built a finite-state-machine sequencer based on the work done by Rory Mangles TinyTim project. He finished building some multiplexers and demultiplexers, and it appears he may be using a whole bank of 14 wall switches for address, input and control functions. For the output display, he assembled a panel using LED’s recovered from a $1 Christmas light string. Something seems amiss with his LED driver, though — 2mA with LED on and >2.5mA with LED off. The LED appears to be connected across the collector and emitter of the PNP transistor. Chime in with your comments.

This build seems to be shaping along the lines of the Megaprocessor that we’ve swooned over a couple of times in the past. Keep at it, [Mark]!

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