ZX Spectrum

47 Articles

FPGA Raises Component Video From A Sinclair ZX Spectrum

May 25, 2020 by 39 Comments

An abiding memory of the early-80s heyday of 8-bit computing for many is operating their computer from the carpet in front of the family TV. While the kids in the computer adverts had parents who bought them a portable colour telly on which to play Jet Set Willy, the average kid had used up all the Christmas present money on the computer itself. The cable would have been an RF connection to the TV antenna socket, and the picture quality? At the time we thought it was amazing because we didn’t know any different, but with the benefit of nearly 40 years’ hindsight, it was awful.

For ZX Spectrum owners in 2020 a standard modification is to bring out a composite video signal, but [c0pperdragon] has gone a step or two beyond that with a component video interface. And this isn’t a mod in which the signals are lifted from the Spectrum’s colour encoder circuitry, instead it uses an FPGA hooked directly to the ULA chip to generate the component video itself.

The Altera chip sits on a little PCB designed to occupy the footprint of the original Astec modulator, and sports a neat bundle of wires hooked up to the various Spectrum signals it needs. There are a couple of jumpers to select the output type and resolution, it supports YPbPr or RGsB outputs and both 288p and 576p. If you think perhaps it looks a little familiar, that’s because it’s the sister project of an earlier board for the Commodore 64. So if you have a Spectrum and are annoyed by UHF and PAL, perhaps it’s worth a look.

Download A Bit Of Sinclair History

April 6, 2020 by 14 Comments

If you are a devotee of the Sinclair series of 8-bit home computers then a piece of news from the Centre For Computing History in Cambridge may be of interest to you, they’ve released a copy of the ROM from their ZX Spectrum prototype. This machine surfaced last year as part of a donation form the company originally contracted to write the Spectrum ROM and has been given pride of place int heir exhibition ever since. They’ve been doing some very careful work on it, and while The Register reports they can’t yet make the board boot, they have extracted the code for study. In the video below the break, we see it running on the Speccy emulator on an older Windows PC.

The ROM comes with an invitation to the ZX Spectrum community to analyze it against the stock version, in the hope of revealing ossified fragments of code such as that for the Microdrive storage peripheral which never made it into the stock Spectrum. But should you simply want to try your favorite games with the earliest possible version of the ROM, you can do that too.

We covered the machine’s emergence last year, meanwhile, if you haven’t been to the Centre for Computing History yet, we suggest you take a look at our review from a few years ago.

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The ZX Spectrum Next Arrives

February 27, 2020 by 34 Comments

Sinclair Research was best known in the United States for the tiny ZX80, and the ZX81, under its Timex branding. However, they also made the ZX Spectrum which had many features that were — at the time — unusual. A few years ago there was a Kickstarter to recreate a modern version of the Spectrum, and [Nostalgia Nerd’s] new ZX Spectrum Next has finally arrived. As you can see in the first part of the hour-long video he was very excited about it. Almost too excited for YouTube.

The new incarnation of the Spectrum claims to be fully compatible with the original but also offers improved graphics modes, SD cards instead of tape, and an optional 7 MHz clock speed. The 512K of RAM would have been sinfully luxurious back in the day when the original model came with 16K, although the most iconic Spectrums would be the 48K models. The new version even has the option of taking a Raspberry Pi Zero to act as an accelerator.

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Spectrum Chiptunes On An STM

June 7, 2019 by 5 Comments

Some of us here at Hackaday are suckers for a bit of chiptune music as the backdrop for many excellent times. The authentic way to create chiptunes is of course the original hardware, but in 2019 it’s far more common to do so with an emulator on a modern computer. That computer doesn’t have to sport a high-end processor and desktop operating system though, as [Deater] shows us with his ZX spectrum chiptune player on an STM32L46G Discovery board.

The impetus for the project came he tells us while teaching students to code simple sine wave music players, having code already in the bag for emulating the classic AY-3-8910 sound chip on the Raspberry Pi and the Apple II he decided to port that to the STM32L476 dev board. An earlier version used the internal DAC, but this was refined to send I2S data to an external DAC. The code can be had from GitHub (confusingly buried among code for an LED driver), and we’ve attached a video below of it playing some chiptune goodness.

Of course, Sinclair chiptunes don’t grab all the limelight. There have been plenty of Nintendo and Sega players too. You might also recognize [Deater] from his non-chiptune work, porting Portal to the Apple ][.

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Stick Your Own Samples In The Cheetah SpecDrum

May 21, 2019 by 10 Comments

The Sinclair ZX Spectrum was a popular computer in the 8-bit era, and particularly so in its homeland of the United Kingdom. It was known more for its low cost than its capabilities, but it gained many add-ons over the years. One of those was the Cheetah SpecDrum, which turned the Spectrum into a rudimentary drum machine. [PianoMatt] wasn’t happy with the original drum samples, so he set about loading a custom kit into the SpecDrum.

The SpecDrum software initially came with extra sample tapes, so [PianoMatt] knew it was an achievable task to load in custom samples. Starting by loading the software in an emulator, the RAM was then exported as raw data and loaded up in Audacity. After some experimentation, it was determined the samples were stored in 8-bit format at a sample rate of approximately 20 kHz. With this figured out, it was then possible to load replacement samples directly into RAM through the emulator.

However, this wasn’t enough for [PianoMatt]. Further digging enabled him to reverse engineer the format of the replacement sample tapes. Armed with this knowledge, [PianoMatt] then generated his own tape, complete with proper headers and labels for each drum sound.

It’s a tidy effort to bring a more modern sound to a now positively ancient piece of hardware. We’d love to hear a track with drums courtesy of the SpecDrum, so we’ll keep an ear out on Soundcloud. Mucking around with old sound hardware is a popular pastime in these parts – we’ve even seen people go so far as to build bespoke Sega chiptune players from scratch. 

Creating 8-bit Games With The Multi Platform Arcade Game Designer

March 29, 2019 by 8 Comments

Creating a game from scratch can be hard work. There are concepts to be designed, coding to be done, and art to be created to make it all happen. However, it doesn’t always have to be quite so difficult. There are a variety of development tools that allow budding game designers to get started with a point-and-click approach. [Jonathan Cauldwell] has come up with just such a tool that lets you do just that, for a variety of 8-bit platforms.

[Jonathan]’s project is called the Multi Platform Arcade Game Designer, so named for its ability to create games for several 8-bit systems of yesteryear. Currently, the Spectrum, Amstrad CPC, and Acorn Atom are all supported, with plans to add more down the track.

Creating a game is a simple affair, which [Jonathan] explores in a video tutorial series. Sprite and background editors are built into the software. Scripts can be automatically generated to create a wide variety of basic game types, from scrolling shoot-em-ups to classic platformers. There’s also functionality that allows advanced users to add further functionality by supplying some of their own code.

If point-and-click isn’t for you, you can always forge your ZX Spectrum games the classic way, with assembly and BASIC. Video after the break.

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The Primordial Sinclair ZX Spectrum Emerges From The Cupboard

March 4, 2019 by 12 Comments

The Centre for Computing History in Cambridge, UK, receive many donations from which they can enrich their collection and museum displays. Many are interesting but mundane, but the subject of their latest video is far from that. The wire-wrapped prototype board they reveal with a flourish from beneath a folded antistatic mat is no ordinary computer, because it is the prototype Sinclair ZX Spectrum.

It came to the museum from Nine Tiles, a local consultancy firm that had been contracted by Sinclair Research in the early 1980s to produce the BASIC ROM that would run on the replacement for their popular ZX81 home microcomputer. The write-up and the video we’ve placed below the break give some detail on the history of the ROM project, the pressures from Sinclair’s legendary cost-cutting, and the decision to ship with an unfinished ROM version meaning that later peripherals had to carry shadow ROMs with updated routines.

The board itself is a standard wire-wrap protoboard with all the major Spectrum components there in some form.  This is a 16k model, there is no expansion connector, and the layout is back-to-front to that of the final machine. The ULA chip is a pre-production item in a ceramic package, and the keyboard is attached through a D connector. Decent quality key switches make a stark contrast to the rubber keys and membrane that Spectrum owners would later mash to pieces playing Daley Thompson’s Decathlon.

This machine is a remarkable artifact, and we should all be indebted to Nine Tiles for ensuring that it is preserved for those with an interest in computing to study and enjoy. It may not look like much, but that protoboard had a hand in launching a huge number of people’s careers in technology, and we suspect that some of those people will be Hackaday readers. We’ll certainly be dropping in to see it next time we’re in Cambridge.

If you haven’t been to the Centre for Computing History yet, we suggest you take a look at our review from a couple of years ago. And if prototype home computers are your thing, this certainly isn’t the first to grace these pages.

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