Putting The Sega Teradrive Into Overdrive

October 9, 2018 by Drew Littrell 25 Comments

During the 80s and 90s it seemed like Japan got all the good stuff when it came to videogames. In the US there were consoles called the NES, the TurboGrafx-16, and the Genesis. While in Japan they had cooler names like: the Famicom, the PC Engine, and the Mega Drive. The latter was incorporated into a plethora of different form factors, including the little known IBM PC/Mega Drive combo known as the Sega Teradrive. Finding a rare Japanese 1990s PC stateside is a feat in and of itself, and thanks to an electronics hobbyist named [Ronnie] there is at least one Teradrive out there still running strong thanks to an upgraded CPU mod.

In theory, the Sega Teradrive was a dream-machine; combining the utility of an IBM PC with the fun of a Sega Mega Drive. The dual functionality extended to the video modes where both VGA and composite video were supported. However, the reality was that the final design was less than desirable. The Teradrive shipped in 1991 with an Intel 80286, 16-bit processor which was already two processor generations behind at the time. The meager 10Mhz clock speed was on the lower end of the performance spectrum which meant that many DOS titles ran poorly…or not at all.

Not satisfied with those specs, [Ronnie] modded his Teradrive with an adapter board containing an Intel 80486 processor clocked at 66Mhz. The upgrade, accompanied with a complete re-cap of the motherboard, brings the IBM PC to 486DX status. This opened up a few new possibilities including the Thundercats Demo in the video below:

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Reading Old Data Tapes, The Hard Way

October 7, 2018 by Dan Maloney 29 Comments

Those who were around for the pre-floppy days of computer mass storage were likely to have made the mistake of slipping a cassette tape containing data into a stereo tape deck. Instead of hearing the expected Awesome Mix, the speakers gave off an annoying bleat, warbling between two discordant tones and no doubt spoiling the mood.

What you likely heard was the Kansas City standard, an early attempt to provide the budding microcomputer industry with a mass-storage standard. It was successful enough that you can still find KCS tapes in need of decoding to this day. That job would be a snap with a microcontroller, which is exactly why [matseng] chose to do it the hard way and built a KCS decoder with nothing but discrete components.

The goal was to decode the frequency-shift-keyed (FSK) signal into an 8-bit parallel output, and maybe drive a seven-segment display as the characters came off the tape at a screaming 300 baud. Not an IC is in sight in the schematics; as [matseng] says, it’s nothing but “Qs, Rs, and Cs.” All the amps, flip-flops, and counters needed are built from a forest of transistors, and even the seven-segment display is a DIY affair of LEDs in a 3D-printed and hot-glue frame. The video below shows the display doing its best to show the alphanumeric characters encoded on the audio tape. And for who absolutely need a dose of Arduino, [matseng] used one along with a dead-bug low-pass filter to emulate KCS signals, for easier development.

We always appreciate hackers who take the road less traveled to arrive at a solution, but if you’re pressed for time to decode some KCS tapes, fear not – all you need is a PC and Audacity.

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Displaying Bitmaps On The Apple II

October 5, 2018 by Zoe Skyforest 34 Comments

The Apple II was the popular darling that truly kicked off the ascention of the company that would later bring you darlings such as the iMac, iPod, and iPhone. The brainchild of the legendary Steve Wozniak, it was a low-cost home computer that made use of some interesting compromises to create video output with the bare minimum components. This can make it difficult if you want to output full-bitmap graphics on the Apple II – but it is certainly possible.

[cybernesto] set about completing this task, and released VBMP on GitHub. Programmed in assembly, it builds upon the work of democoder Arnaud Cocquière to display bitmap images on the vintage 6502-powered machine. Capable of displaying monochrome images in 560 x 192 or sixteen colors in 140 x 192, it loads slowly but does get the job done.

We’ve seen similar development underway elsewhere, too – on this vintage satellite tracker project. [Keplermatic] reports that their code runs at a similar speed to the VBMP loader, despite doing several things differently. It’s also available over at GitHub, for your reading pleasure.

If you’re looking to achieve something similar with your vintage hardware, it’s worth a look. Having the source available makes integrating it into further projects a snap. Learning to program these older machines can be challenging, but that’s half the fun – and when you build something awesome, be sure to drop it on the tips line.

Ants, Dirt, Rain, And The Commodore 64 That Wouldn’t Quit

October 3, 2018 by Dan Maloney 34 Comments

Some electronics gear is built for the roughest conditions. With rugged steel cases, weatherproof gaskets, and cables passing through sealed glands, these machines are built to take the worst that Mother Nature can throw at them, shrugging off dust, mud, rain, and ice. Consumer-grade computers from the start of the home PC era, however, are decidedly not such machines.

Built to a price point and liable to succumb to a spilled Mountain Dew, few machines from that era that received any kind of abuse lived to tell the tale. Not so this plucky Commodore 64C, which survived decades exposed to the elements. As [Adrian Black] relates in the video below, this machine was on a scrap heap in an Oregon field, piled there along with other goodies by one of those “pickers” that reality TV loves so much. The machine was a disaster. It hadn’t been soaked in oil, but it was loaded with pine needles and an ant colony. The worst part, though, was the rust. The RF shielding had corroded into powder in some places, leaving reddish rust stains all over the place. Undeterred, [Adrian] gave the machine a good bath, first in water, then in isopropanol. Liberal applications of Deoxit helped with header connections, enough to see that the machine miraculously booted. It took some finagling, especially with the 6526 I/O controller, but [Adrian] was eventually able to get everything on the motherboard working, even the sound chip.

Whether this machine survived due to good engineering or good luck is debatable, but it’s a treat to see it come back to life. We hope a full restoration is in the works, not least as a way to make up for the decades of neglect.

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Pristine Apple I Sells At Auction For A Jaw-Dropping Price

October 1, 2018 by Dan Maloney 29 Comments

If you think Apple products are overpriced now, wait until they’re 50 years old.

This original Apple I recently sold at auction for $375,000, making it one of the most expensive 6502-based computers in history. Given that only something like 60 or 70 of the machines ~~were ever made~~ are known to exist, most built by hand by [Jobs] and [Wozniak], it’s understandable how collectors fought for the right to run the price up from the minimum starting bid of $50,000. And this one was particularly collectible. According to the prospectus, this machine had few owners, the most recent of whom stated that he attended a meeting of the legendary Homebrew Computer Club to see what all the fuss was. He bought it second-hand from a coworker for $300, fiddled with it a bit, and stashed it in a closet. A few years later, after the Apple ][ became a huge phenomenon, he tried to sell the machine to [Woz] for $10,000. [Woz] didn’t bite, and as a result, the owner realized a 125,000% return on his original investment, before inflation.

The machine was restored before hitting the auction block, although details of what was done were not shared. But it couldn’t have been much since none of the previous owners had even used the prototyping area that was so thoughtfully provided on the top edge of the board. It was sold with period-correct peripherals including a somewhat janky black-and-white security monitor, an original cassette tape interface, and a homebrew power supply. Sadly, there’s no word who bought the machine – it was an anonymous purchase.

Hackers, check your scrap bins. Anything hanging out there that might be worth six figures in a few decades? It’s unlikely, but if you get lucky, hacking just might turn into your retirement plan.

Thanks to [my wife] for the tip on this one.

Microsoft Releases Crown Jewels — From 1982!

October 1, 2018 by Al Williams 45 Comments

If you look back 30 or so years ago, it wasn’t clear what was going to happen with personal computers. One thing most people would have bet on, though, was that CP/M — the operating system from Digital Research — would keep growing and power whatever new machines were available. Except it didn’t. MS-DOS took over the word and led — eventually — to the huge number of Windows computers we know today. Microsoft has released the source code to MS-DOS 1.25 and 2.0 on GitHub.

Microsoft — then another fledgling computer company — had written some BASIC interpreters and wanted in on the operating system space. They paid the princely sum of $75,000 to Seattle Computer Products for something called QDOS written by [Tim Paterson]. Rebranded as MS-DOS, the first version appeared in late 1981 and version 1.25 was out about a year later.

While you might not think having MS-DOS source code is a big deal, there’s still a lot of life left in DOS and it is also interesting from an educational and historical perspective. If you don’t want to read x86 assembly language, there’s also the BASIC source for the samples (paradoxically, in the bin subdirectory) along with compiled COM files for old friends like EDLIN and DEBUG.

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A Nibble And A Half Of Wooden Bits

September 25, 2018 by Brian McEvoy 8 Comments

If you are familiar with binary, what would you need to teach someone who only knows decimal? If you do not know how to count in binary, let us know if the video below the break helps you understand how the base-2 number system works. If learning or counting binary is not what you are interested in, maybe you can appreciate the mechanics involved with making a counter that cycles through all the ones and zeros (links to the video shown below). The mechanism is simple enough. A lever at the corner of each “1” panel is attached off-center, so it hangs when it is upside-down, then falls to the side when it is upright, so it can swivel the adjacent panel.

Perhaps this is a desktop bauble to show off your adeptness at carpentry, or skills with a laser cutter, or 3D printer. No matter what it is made out of, it will not help you get any work done unless you are a teacher who wants to demonstrate the discrete nature of binary. If wood and bits are up your alley, we have a gorgeous binary driftwood clock to feast your eyes on. Meanwhile if analog methods of working digital numbers suit you, we have binary math performed with paper models.

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