BBC Micro

19 Articles

The BBC Micro, Lovingly Simulated In VR

April 14, 2024 by 5 Comments

The BBC Micro was many peoples’ first exposure to home computing, and thanks to [Dominic Pajak], you can fire up this beloved hardware in WebXR. Is it an emulator? Yes, but it’s also much more than that.

The machine, the CRT, the keycaps, and even the sounds of the original keypresses are all brought to life as accurately as possible. The result is not just an emulator. It’s a lovingly-made BBC Micro simulator you can use with a VR headset. Or just use your browser and type on your real keyboard if you like.

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BBC Basic Is Back In A Big Way

November 28, 2023 by 70 Comments

The BBC has a long history of teaching the world about computers. The broadcaster’s name was proudly displayed on the BBC Micro, and BBC Basic was the programming language developed especially for that computer. Now, BBC Basic is back and running on a whole mess of modern platforms.

BBC Basic for SDL 2.0 will run on Windows, MacOS, x86 Linux, and even Raspberry Pi OS, Android, and iOS. Desktop versions of the programming environment feature a BASIC editor that has syntax coloring for ease of use, along with luxury features like search and replace that weren’t always available at the dawn of the microcomputer era. Meanwhile, the smartphone versions feature a simplified interface designed to work better in a touchscreen environment.

It’s weird to see, but BBC Basic can actually do some interesting stuff given the power of modern hardware. It can address up to 256 MB of memory, and work with far more advanced graphical assets than would ever have been possible on the original BBC Micro. If you honed your programming skills on that old metal, you might be impressed with what they can achieve with BBC Basic in a new, more powerful context.

If you’re passionate about the BBC and its history with computers, we’ve talked plenty about the BBC Micro in the past, too.

[Thanks to Stephen Walters for the tip!]

A Virus For The BBC Micro

September 12, 2023 by 11 Comments

If you work at all with British software or hardware engineers, you’ll find that there’s an entire generation perhaps now somewhere between their mid-40s and mid-50s, who stand slightly apart from their peers in their background and experience. These were the lucky teenagers who benefited from the British government’s 1980s push to educate youngsters in computing, and who unlike those before or who followed, arrived at university engineering courses fresh from school fully conversant with every facet of a computer from the hardware upwards.

[Alan Pope] is from that generation, and he relates a tale from his youth that wasn’t so out of place back in those days, of how he wrote what we’d now call a simple virus for the BBC Micro. Better still, he’s re-created it.

The post is as much a delightful trip back through that era of microcomputing, including an entertaining aside as he shared an airline journey with BBC Micro designer Chris Turner, and it serves as a reminder of how the BBC Micro’s disk operating system worked. There was a !boot file, which was what would be run from the disk at startup, and his bit of code would subvert that and hide itself in the machine’s so-called sideways RAM. The payload was pretty simple, every 32 soft reboots it would print a “Hello world” message, but it seems that was enough back in 1989 to get him into trouble. The 2023 equivalent works, but we’re guessing no teacher will come for him this time.

If you can’t find a real BBC Micro but still want one on hardware, we’ve brought you an FPGA version in the past.

Reading Floppies With An Oscilloscope

May 20, 2021 by 6 Comments

There’s a lot of data on magnetic media that will soon be lost forever, as floppies weren’t really made to sit in attics and basements for decades and still work. [Chris Evans] and [Phil Pemberton] needed to read some disks that reportedly contained source code for several BBC Micro games, including Repton 3. They turned to Greaseweazle, an interface board that can dump just about any kind of floppy disk if it is attached to the right drive. The problem is that Greaseweazle couldn’t read the disks due to CRC errors. Time to break out the oscilloscope and read the disk manually, which is what they did.

Greaseweazle provides a nice display of read sectors and shows timing coming from the floppy read head. The disk in question looked good with reasonably clean timing clocks except in the area of one sector. At that point, the clocks degenerated into noise. Looking on the disk, it was easy to see why. The actual media had a small dent in it.

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The Tube Map, In Glorious 8-Bit!

February 15, 2021 by 6 Comments

There was a time when visitors to London would carry an A to Z map to navigate the city’s Undergound railway system, referring to the iconic London Transport map printed on its back as they did so. Now it’s likely they’ll do the same with their smartphones, with apps ranging from simple analogues of the printed version through to fully annotated route planners with up to the minute train information. Is this a new technology, something only possible in the last decade? Serial British rail YouTuber [Geoff Marshall] thinks otherwise, and has programmed a Tube map on a vintage BBC Micro.

We don’t expect anyone to heft a pile of vintage hardware onto the Central Line at rush hour even though in reality he’s running it on an emulator due to his real BBC Micro being kaput. Perhaps someone should drop him a line about capacitor replacement in that power supply. But it does provide an entertaining jaunt back into afternoons in a 1980s school computer lab, with MOVE, DRAW, and PLOT commands as he wrestles with the limited colour palette of MODE 2.  The result only covers Tube Zone 1, or the very centre of London, so to visit London Hackspace you’ll have to remember to take the Bakerloo line northbound out to Zone 4 and disembark at Wembley Central.

Happily as you can see in the video below the break he enlists the help of a friend to run it on real hardware. He posted the code as a comment to the video but it’s really hard to find. Try this direct link and scroll down, it should be the first comment but you need to click “Read more” to unfold the code. We think the Tube Map would make a great test for any retrocomputer, so we look forward to this feat being repeated.

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A Lowly 8-Bit Micro Busts Copy Protection From The 16-Bit Era

July 16, 2020 by 6 Comments

When floppy disks were the data storage medium of choice, software companies and in particular game developers came up with ever more inventive ways to make them difficult to copy. Tinkering at the edges of the disc format standards didn’t come cheap though, and for example the Dungeon Master game for the Atari ST was reported as using $40,000 worth of custom hardware to achieve its so-called “fuzzy bit” technique. [Chris Evans] set out to recreate it, not by building a modern version of the custom hardware, but by doing it the hard way, with an early-1980s 8-bit BBC Micro home computer.

One could be forgiven for thinking that a computer sporting a 2 MHz 6502 would be unable to manage this task without extra hardware, and were it simply the 6502 itself you would of course be right. So to get anywhere he had to get creative with the Beeb’s built-in peripherals. Eschewing the floppy controller it was hooked up directly to the parallel port, and after a voltage problem courtesy of the drive’s termination resistors we’re taken through some of the 6522 VIA’s different modes in order to achieve a higher speed data burst than would normally be possible. All of these approaches hit the buffers though, until he looks at the 6845 video chip and uses its video output as a very fast shift register. With a custom cable and some work on special video modes, a home computer that would have cost several hundred dollars in the early 1980s can do the work of $40,000 custom hardware from later in the decade. Colour us impressed!

If you’d like to know more about the Dungeon Master copy protection, we’ve been there in the past.

BBC Micro header image: StuartBrady / Public domain.

How Did They Get Sampled Sounds From An SN76489 8-bit Sound Chip?

June 5, 2020 by 23 Comments

If you were lucky and had well-off parents in the early 1980s, your home computer had a sound chip on board and could make music. There were a variety of chips on the market that combined in some form the tone generators and noise sources of a synthesiser, but without the digital-to-analogue converters of later sound chips designed for sampled audio. They gave birth to chiptune music, but that was all they were made to do. The essence of a hack lies in making something perform in a way it was never intended to, and some game developers for the Acorn BBC Micro had its SN76489 producing sampled audio when it should never have been possible. How did they do it? It’s a topic [Chris Evans] has investigated thoroughly, and his write-up makes for a fascinating explanation.

So, how can a set of audio tone generators be turned into a sampled audio player, and how can it be done when the CPU is a relatively puny 6502? There’s no processor bandwidth for clever Fourier transform tricks, and 1980s tech isn’t set up for high data bandwidths. The answer lies in making best use of the controls the chip does offer, namely frequency and volume of a tone. A single cycle of a tone can be given a volume, and thus can be treated as a single sample of an unintended DAC. By using a tone frequency well above the audio range a suitable sample frequency can be found, and thus an audio stream can be played. The write-up has links to some examples in an emulator, and while they’re hardly hi-fi they’re better than you might expect for the hardware involved. Still, even at that they don’t approach this amazing 48kHz playback on a Commodore 64.

Header: SN76489, on a Colecovision console motherboard. Evan-Amos / Public domain.