Emulating a Hard Drive With The Raspberry Pi

[Chris] recently moved a vintage IBM 5150 – the original PC – into his living room. While this might sound odd to people who are not part of the Hackaday readership, it actually makes a lot of sense; this PC is a great distraction-free writing workstation, vintage gaming machine, and looks really, really cool. It sat unused for a while, simply because [Chris] didn’t want to swap out piles of floppies, and he doesn’t have a hard drive or controller card for this machine. After reviewing what other retrocomputer fans have done in this situation, he emulated a hard drive with a Raspberry Pi.

The traditional solution to the ‘old PC without a hard drive’ problem is the XTIDE project. XTIDE is a controller card that translates relatively new IDE cards (or an emulated drive on another computer) as a hard drive on the vintage PC, just like a controller card would. Since a drive can be emulated by another computer, [Chris] grabbed the closest single board computer he had on hand, in this case a Raspberry Pi.

After burning an EPROM with XTIDE to drive an old network card, [Chris] set to work making the XTIDE software function on the Raspberry Pi side of things. The hardware on the modern side of the is just a Pi and a USB to RS232 adapter, set to a very low bitrate. Although the emulated drive is slow, it is relatively huge for computer of this era: 500 Megabytes of free space. It makes your head spin to think of how many vintage games and apps you can fit on that thing!

Vulcan 74: A Masterpiece of Retro Engineering

[Radical Brad] has played around with FPGAs, video signals, and already has a few astonishing projects of bitbanged VGA on his resume. Now he’s gone insane. He’s documenting a build over on the 6502.org forums of a computer with Amiga-quality graphics built out of nothing but a 65C02, a few SRAM chips, and a whole pile of logic chips.

The design goals for this project are to build a video game system with circa 1980 parts and graphics a decade ahead of its time. The video output is VGA, with 400×300 resolution, in glorious eight-bit color. The only chips in this project more complex than a shift register are a single 65c02 and a few (modern) 15ns SRAMs. it’s not a build that would have been possible in the early 80s, but the only thing preventing that would be the slow RAM chips of the era.

So far, [Radical] has built a GPU entirely out of 74-series logic that reads a portion of RAM and translates that to XY positions, colors, pixels, and VGA signals. There’s support for alpha channels and multiple sprites. The plan is to add sound hardware with support for four independent digital channels and 1 Megabyte of sample memory. It’s an amazingly ambitious project, and becomes even more impressive when you realize he’s doing all of this on solderless breadboards.

[Brad] will keep updating the thread on 6502.org until he’s done or dies trying. So far, it’s looking promising. He already has a bunch of Boing balls bouncing around a display. You can check out a video of that below.

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Engineers Create Super-Hard Whack-a-Mole

Is your latest project driving you mad? Are you subject to occasional fits of rage? This project might help: for a class called elecanisms at Olin College, [Forrest] and a team of three other students made a whack-a-mole arcade game that lets you vent your rage on a helpless furry animal by whacking it with a large hammer. He built most of it from scratch, creating his own solenoid driver and LED sensor board. However, there is a twist in here that gives the moles a fighting chance: there is an accelerometer built into the hammer that lets them know that your heavy hammer of doom is approaching.

Will they escape before your righteous wrath descends upon them? That depends on how you decide to set it up, and how merciful you want to be. The build even includes a coin-operated pay-to-play slot. They kept the cost low at a penny, but this is just begging to be installed at the local pub to rake in those quarters.

This course has been the source of a few projects that we have featured before on Hackaday, including the Confectionary Canon, which tracks your face and fires marshmallows right into your gaping maw.

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DIY Punch Card System Despite Hanging Chads

Sometimes you just have parts lying around and want to make something out of them. [Tymkrs] had a robot paper cutter, so naturally they made punch cards. But then, of course, they needed a punch card reader, so they made one of those too. All with stuff lying around the shop.

The Silhouette Portrait paper cutter is meant for scrapbooking, but what evokes memories of the past more than punchcards? To cut out their data, rather than cute kittens or flowers, they wrote some custom code to turn ASCII characters into rows of dots. And the cards are done — you just have to clean up the holes that didn’t completely cut. These are infamously known as hanging chads.

The reader is made up of a block of wood, with a gap for the cards and perpendicular holes drilled for LEDs and photoresistors. This is cabled to a Propeller dev board with some simple firmware. We would have used photodiodes or phototransistors, because that’s what’s in our junk box (and because they have faster reaction time), but when you’ve got lemons, make lemonade.

OK, now that you’ve got a punch card reader and writer, what do you do with it? Password storage comes to mind.

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Dumping Old PROMs With New Hardware

[ijsf] recently came across a very old synthesizer from a defunct West German company. This was one of the first wavetable synths available, and it’s exceptionally rare. Being so rare, there isn’t much documentation on the machine. In an attempt at reverse engineering, [ijsf] decided to dump the EPROMs and take a peek at what made this synth work. There wasn’t an EPROM programmer around to dump the data, but [ijsf] did have a few ARM boards around. It turns out building a 27-series PROM dumper is pretty easy, giving [ijsf] an easy way to dig into the code on this machine.

The old EPROMs in this machine have 5v logic, so [ijsf] needed to find a board that had a ton of IOs and 5v tolerant inputs. He found the LPC2148, which has a nice USB system that can be programmed to dump the contents of a PROM over serial. Interfacing the PROM is as simple as connecting the power and ground, the address lines, data, and the signal lines. After that, it’s just a matter of stepping through every address according to the timing requirements of the PROM. All the data was dumped over a serial interface, and in just a few seconds, [ijsf] had 32768 bytes of ancient data that made this old synth tick.

Typewriter Types, Plays Music

[Chris Gregg] had a dream. He wanted to convert use a typewriter as a printer. Sure this has been done before, but [Chris] wanted to create his own version. He picked up a 60’s era Smith Corona electric typewriter, with the hopes of driving its key switches with a computer. You can imagine his surprise when he discovered the keys were not electric switches at all, but a complex mechanical system which triggered a clutch to strike the actual paper. Realizing this was not going to be a simple wiring job, [Chris] set the project aside, where it remained for several years.

A conversation with [Bruce Molay], a coworker at Tufts University reignited [Chris’] interest in project. [Bruce] suggested using solenoids to press the keys. [Chris] dove in, and quickly had 48 solenoids on hand. The first problem was mounting the solenoids on the keys. [Chris’] roommate happens to be [Derek Seabury], president of Artisan’s Asylum Hackerspace. [Derek] created an acrylic frame which holds the solenoids and fits directly over the typewriter’s keyboard. This meant that no modifications needed to be made to the typewriter itself. Simply lift off the solenoid array and you’re ready to rock like it’s 1965.

The next step was driving all those solenoids. For that, Chris worked with [Kate Wasynczuk], one of his students at Tufts. [Chris] designed a board using Texas Instruments  TPIC6A595 shift registers. The TIPC “power logic” series work like regular 74 series logic, but have seriously beefy outputs. These chips can handle up to 50 volts and 1.5 amps pulsed output current – plenty for [Chris’] 24 volt solenoids. [Chris] taught himself schematic entry and PCB layout in Eagle. After only two tries, he had a working board from OSHPark.

An Arduino Uno converts serial over USB output to a bit stream ready to clock into the shift registers. On the computer side, [Chris] wrote up a basic CUPS driver which allows him to print from his Macbook. The perfect demo for this project turned out to be musical. Click past the break to see The Smith Corona perform “The Typewriter Symphony”, by Leroy Anderson. This may be the first time this particular piece of music has been performed with actual words being typed, rather than random keys.

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Discrete Transistor Computer Is Not Discreet

Every few years, we hear about someone building a computer from first principles. This doesn’t mean getting a 6502 or Z80, wiring it up, and running BASIC. I’m talking about builds from the ground up, starting with logic chips or even just transistors.

[James Newman]’s 16-bit CPU built from transistors is something he’s been working on for a little under a year now, and it’s shaping up to be one of the most impressive computer builds since the days of Cray and Control Data Corporation.

The 10,000 foot view of this computer is a machine with a 16-bit data bus, a 16-bit address bus, all built out of individual circuit boards containing single OR, AND, XOR gates, decoders, multiplexers, and registers.  These modules are laid out on 2×1.5 meter frames, each of them containing a schematic of the computer printed out with a plotter. The individual circuit modules sit right on top of this schematic, and if you have enough time on your hands, you can trace out every signal in this computer.

The architecture of the computer is more or less the same as any 16-bit processor. Three are four general purpose registers, a 16 bit program counter, a stack pointer, and a status register. [James] already has an assembler and simulator, and the instruction set is more or less what you would expect from a basic microprocessor, although this thing does have division and multiplication instructions.

The first three ‘frames’ of this computer, containing the general purpose registers, the state and status registers, and the ALU, are already complete. Those circuits are mounted on towering frames made of aluminum extrusion. [James] already has 32 bytes of memory wired up, with each individual bit having its own LED. This RAM display will be used for the Game of Life simulation once everything is working.

While this build may seem utterly impractical, it’s not too different from a few notable and historical computers. The fastest computer in the world from 1964 to ’69 was built from individual transistors, and had even wider busses and more registers. The CDC6600 was capable of running at around 10MHz, many times faster than the estimated maximum speed of [James]’ computer – 25kHz. Still, building a computer on this scale is an amazing accomplishment, and something we can’t wait to see running the Game of Life.

Thanks [aleksclark], [Michael], and [wulfman] for sending this in.