Modern In-Circuit Emulator For The 6809

July 19, 2024 by Alexander Rowsell 12 Comments

The Motorola 6809, released in 1978, was the follow-up to their 6800 from four years earlier. It’s a powerful little chip with many 16-bit features, although it’s an 8-bit micro at heart. Despite its great improvements over the 6800, and even technical superiority over the Z80 and 6502 (hardware multiply, for example!), it never reached the same levels of success that those chips did. However, there are still some famous systems, such as the TRS-80 Colour Computer, which utilized the chip and are still being hacked on today. [Ted] is clearly a fan of the 6809, as he used a Teensy 4.1 to create a cycle-exact, drop-in 6809 emulator!

A small interposer board rearranges the Teensy pinout to match the 6809, as well as translating voltage levels from 3.3V to 5V. With careful design, the Teensy matches the cycle diagrams in the Motorola datasheet precisely, and so should be able to run any applications written for the chip! A great test was booting Extended Colour BASIC for the TRS-80 CoCo 2 and running some test BASIC programs. Any issues with opcode decoding or timing would certainly be exposed while running an interpreted language like BASIC. After this successful test, it was time to let the Teensy’s ARM Cortex-M7 rip and see what it could do.

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It’s A CoCo! No, It’s An Apple II!

March 2, 2024 by Jenny List 2 Comments

Original retrocomputing hardware is now decades old and showing its age, so the chances are it’s more common in 2024 to experience a machine from the 1970s or 1980s by way of an emulator on a modern machine than it is on the real hardware. There’s another more limited emulation scene as similar 8-bit machines emulate each other, for example when the very similar Dragon 32 and Tandy CoCo have a go at each other’s software. Rarest of them all though is when one classic machine emulates another with a different architecture, but that’s exactly what’s happened with [DragonBytes], who has persuaded a Tandy CoCo to emulate an Apple II.

The two machines have significant hardware differences, but we’re guessing that the project is helped a little by the Motorola 6809 in the CoCo and the MOS 6502 in the Apple having both in a sense been different visions of a successor to the Motorola 6800. Thus their architectures while different, are not diametrically opposed. The other hardware is certainly not so similar though, with Moto’s 6847 display chip in the Tandy being far more conventional than Steve Wozniak’s clever NTSC hacks to achieve a color display for minimal cost on the Apple.

The project is written in assembler, and doesn’t by any means claim to support all Apple modes, or be cycle accurate. But it’s a hugely impressive achievement nevertheless.

The CoCo has an enthusiastic following, and has appeared here a few times in the past. We particularly like this video player.

Render Yourself Invisible To AI With This Adversarial Sweater Of Doom

October 20, 2022 by Dan Maloney 57 Comments

Ugly sweater season is rapidly approaching, at least here in the Northern Hemisphere. We’ve always been a bit baffled by the tradition of paying top dollar for a loud, obnoxious sweater that gets worn to exactly one social event a year. We don’t judge, of course, but that’s not to say we wouldn’t look a little more favorably on someone’s fashion choice if it were more like this AI-defeating adversarial ugly sweater.

The idea behind this research from the University of Maryland is not, of course, to inform fashion trends, nor is it to create a practical invisibility cloak. It’s really to probe machine learning systems for vulnerabilities by making small changes to the input while watching for changes in the output. In this case, the ML system was a YOLO-based vision system which has little trouble finding humans in an arbitrary image. The adversarial pattern was generated by using a large set of training images, some of which contain the objects of interest — in this case, humans. Each time a human is detected, a random pattern is rendered over the image, and the data is reassessed to see how much the pattern lowers the object’s score. The adversarial pattern eventually improves to the point where it mostly prevents humans from being recognized. Much more detail is available in the research paper (PDF) if you want to dig into the guts of this.

The pattern, which looks a little like a bad impressionist painting of people buying pumpkins at a market and bears some resemblance to one we’ve seen before in similar work, is said to work better from different viewing angles. It also makes a spiffy pullover, especially if you’d rather blend in at that Christmas party.

Awakening A Dragon From Its Slumber

January 12, 2020 by Jenny List 18 Comments

For all the retrocomputing fun and games we encounter in our community, there are a few classic microcomputers that rarely receive any attention. Usually this is because they didn’t sell well and not many have survived, or were simply underwhelming machines that haven’t gathered a huge following today. One that arguably falls within both camps is the Dragon 32, a machine best known in those pre-Raspberry Pi days for being the only home computer manufactured in Wales, and for being nearly compatible with the Tandy Color Computer due to both machines’ designs coming from the same Motorola data sheet. Repeat restorer of retrocomputers, [Drygol], has given a Dragon 32 the full restoration and upgrade treatment, offering us a rare chance to take a look at this computer.

The Dragon arrived with a pile of contemporary books and software, but no power supply. A significant modification was made to the internal PSU board then to allow it to work with an Amiga unit, and the black-on-green Dragon text came up on the TV screen. Recapping and a replacement for a faulty op-amp fixed poor video quality, then it was time for a 64K memory upgrade with some neatly done bodge-wiring. Finally there’s a repair to the very period-looking analogue joystick, and a home-made interface for the more common Atari/Amiga style sticks.

The Dragon may be only a footnote in the history of 8-bit home computing, but with its good expandability and decent quality keyboard it perhaps deserved to reach more homes than it did. This appears to be the first time a Dragon has featured here, though its Tandy CoCo cousin has made it into a few stories.

VCF East: Old Computers, New Games

April 8, 2014 by Brian Benchoff 2 Comments

While the vintage computer festival in Wall, NJ had just about every vintage app you could imagine – multiple varities of *NIXes, pre-Zork Dungeon, BASIC interpreters of all capabilities, and just about every game ever released for 8-bit Commodore systems – there was, perhaps unsurprisingly, a distinct lack of modern programs written for these retro systems. Yes, despite there being people still curled up to keyboards and writing games for vintage systems, modern software was a strange oddity last weekend.

There were two wonderful exceptions, however. The first was Fahrfall, a game for the TRS-80 Color Computer. We’ve seen Fahrfall before when [John Linville] wrote it for the 2012 RetroChallenge Winter Warmup. The game itself is a re-imagining of Downfall for the Atari Jaguar, with the graphics scaled down immensely. The basic idea of the game is to jump down, ledge to ledge, on a vertically scrolling screen. Hit the walls or the bottom, and you’re dead. It’s a great game that probably would have sold well had it been a contemporary release.

Next up is a rather impressive port of Flappy Bird for the TI-99. The video does not do this game justice, although part of that might just be the awesome Amiga monitor used for the display. This game was brought in by [Jeff Salzman] of Vintage Volts who isn’t the author of the game. Honestly, the video doesn’t do the graphics any justice. It really is a great looking port that’s just as addictive as the Android/iDevice original.

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Giving The TRS-80 CoCo A 44 Color Display

August 2, 2012 by Brian Benchoff 25 Comments

As a relic of the early 80s, the TRS-80 Color Computer couldn’t display very many colors. By default, the CoCo could only display 8 colors on the screen at a time, but [John] figured out a way to increase the number of colors displayed using a very simple trick that surprisingly isn’t found in original CoCo games.

The TRS-80 Color Computer uses a Motorola 6847 video display generator to produce color graphics on its display. There are several graphics modes available to CoCo programmers, including a high-resolution black and white mode, and two four-color modes using red, green, blue, and yellow or buff, cyan, magenta, and orange.

These color palettes are extremely limiting, and usually switching between these modes produces a lot of flicker. [John] figured out if he switched the color pallets every 1/60th of a second (i.e. during the vertical blanking interval), he could display 44 colors on the CoCo.

It’s a clever little hack to increase the color palette of the CoCo, and in our opinion should be in the running for winning this season’s Retrochallenge. Sadly, [John] is judge for the Retrochallenge this time around, so he’ll have to settle for earning a Hackaday merit badge.