When A Single Bit Was Enough, Into The Sound Of The ZX Spectrum

January 20, 2022 by Jenny List 8 Comments

It’s normal for a computer in 2022 to come with a fully-featured sound card containing a complete synthesizer as well as high-quality PCM sound recording and playback. It’s referred to as a sound card after the way the hardware first appeared in the world of PCs, but in fact it’s now considered so essential as to be a built-in part of most mainboards. There was a time when computers boasted considerably less impressive sound hardware, and among the chorus of SIDs and AY chips of the perhaps the least well-featured was the original Sinclair ZX Spectrum. Its one-bit sound, a single line on an I/O port, is the subject of a thorough investigation from [Forgotten Computer]. It’s a long video which we’ve placed below the break, but for those with an interest in 8-bit music it should make a for a fascinating watch.

For Sir Clive Sinclair the 1-bit audio must have been welcome as it removed the need for an expensive sound chip and kept the Spectrum to its low price point, but on the face of it there was little more it could do than create simple beeps using Sinclair BASIC’s built-in BEEP command. The video gives us an in-depth look at how interleaving and PWM could be used to create much more complex sounds such as the illusion of multiple voices and even sampled sounds. In particular his technique of comparing the audio output with its corresponding pin on the Sinclair ULA shows the effect of the machine’s simple low-pass filter, though the music was often so close to the edge of what the interface could do that aliasing sounds are often very obvious.

As he demonstrates the various ingenious techniques that game and demo developers used to extract performance from such limited hardware that could even try to compete with the more sophisticated machines even at the same time as their code was running whatever was on the screen, it’s difficult not to come away with immense respect for their skills. If you’ve ever experimented with computer audio then you should try hardware this simple for yourself.

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A Redesigned ZX Spectrum Desktop Computer That Works Surprisingly Well

October 17, 2021 by Jenny List 20 Comments

Retrocomputer enthusiasts will quite often be found pondering the great what ifs of their hobby. What if Commodore had had a half-way decent marketing division is a popular one, but the notoriously penny-pinching ways of Sinclair Research are also a plentiful source. What if Sinclair had won the competition for a computer in UK schools, not only the first time around when Acorn’s BBC Micro scooped the prize, but also what if they’d entered the fray once more in 1983 when there was another chance? [10p6] investigates this possibility, and comes up with a Spectrum desktop computer that you can see in the video below the break.

The first two-thirds of the video is devoted to renders which, while pretty to look at, offer nothing of substance. In the later part though we see a build, putting a Spectrum 48k board, Interface 1, and two Microdrives in a slimline case along with a power supply. Meanwhile a ZX rubber keyboard is mounted stand-alone on the end of a cable. It’s a computer that we know would have been an object of desire for many kids back in the day, and we agree with the video that it could have been integrated onto one board without the need for a separate Interface 1. We feel it’s inevitable though that Sinclair’s cost-cutting would have caused something to go astray and there would certainly have been only one Microdrive, even though we like that separate keyboard a lot.

They claim that the STLs will be available from a Facebook group, however unless you happen to have a set of Microdrives and an Interface 1 to go with your Spectrum that you’re prepared to butcher for the project we’re guessing that the chief interest lies in watching it unfold and that some of the ideas might translate to other platforms. Meanwhile if you’re interested in the Microdrive, we did a teardown on them last year.

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How To Get Into Computer Game Development In 1982

September 26, 2021 by Jenny List 16 Comments

If you are a follower of retrocomputing, perhaps you caught the interactive Black Mirror episode Bandersnatch when it came out on Netflix. Its portrayal of a young British bedroom coder finding his way into the home computer games industry of the early 1980s was of course fictional and dramatised, but for those interested in a real-life parallel without the protagonist succumbing to an obsession with supernatural book there’s a recent epic Twitter thread charting an industry veteran’s path into the business.

An acceptance letter like this from Artic Software would have been the wildest dream of any early-80s bedroom coder.

[Shahid Kamal Ahmad] now has an impressive portfolio spanning his his nearly four decades at the forefront of gaming, but his story starts in 1982 as a diabetic British Pakistani teenager from a not-privileged background in London writing in BASIC on his Atari 400. His BASIC games are good, but not good enough to gain acceptance from a publisher, so he sells his prized BMX bicycle to buy books on Atari 6502 assembler, a coffee percolator, and for curiosity’s sake, [Rodnay Zaks’] Programming the Z80. An obsessive three-month learning of 6502 programming and the Atari’s architecture ensues, and his game Storm in a Teacup sells to Artic Software. He’s a professional game developer.

We follow him through a couple more projects until he arrives at Software Projects in Liverpool to try to sell his game Faces of Haarne, which he secures publishing for but also lands the opportunity of a lifetime. Jet Set Willy is the smash hit of the year on the ZX Spectrum, and they urgently need a Commodore 64 port. Can he do it in four weeks, with a bonus if he manages three? The subsequent descent into high-pressure assembly coding and learning the quirks between two completely different 8-bit architectures is an epic in itself, but he manages it in just a shade over the three weeks and they pay him the bonus anyway. His career in the computer game industry is cemented.

Through this tale the reminders of 1980s Britain are everywhere, far from bring a retro paradise it was a place hollowed out by industrial decline, with very little for those at the bottom of society to be optimistic about. His descriptions of casual racism are hard-hitting, but the group of computer-addicted friends at school is probably something that all teenagers of the era whose interests lay in that direction can relate to. The real hero of the story is probably his mother, who somehow found the resources for that Atari 400 and who provided him with much-needed support and encouragement.

This thread captures a unique and never-to-be repeated era in which a teenager could master an emerging technology and make a living in it without an expensive education. Like Bil Herd’s description of his career at Commodore in the same period, it’s well worth a read.

Farewell Sir Clive Sinclair; Inspired A Generation Of Engineers

September 16, 2021 by Jenny List 74 Comments

It is with sadness that we note the passing of the British writer, engineer, home computer pioneer, and entrepreneur, Sir Clive Sinclair, who died this morning at the age of 81 after a long illness. He is perhaps best known among Hackaday readers for his ZX series of home computers from the 1980s, but over a lifetime in the technology industry there are few corners of consumer electronics that he did not touch in some way.

Sinclair’s first career in the 1950s was as a technical journalist and writer, before founding the electronics company Sinclair Radionics in the 1960s. His output in those early years was a mixture of miniature transistor radios and Hi-Fi components, setting the tone for decades of further tiny devices including an early LED digital watch at the beginning of the 1970s, miniature CRT TVs in the ’70s and ’80s, and another tiny in-ear FM radio which went on sale in the ’90s.

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Finally! The ROM You Wished Your Sinclair Spectrum Had!

November 27, 2020 by Jenny List 10 Comments

If there is one thing that Sir Clive SInclair was famous for, it was producing electronic devices that somehow managed to squeeze near-impossible performance out of relatively meagre components. This gave us some impressive products, but it’s fair to say that sometimes this philosophy pushed the envelope a little too far. Thus even some of the most fondly remembered Sinclair products concealed significant flaws, and this extended to both their hardware and their software.

The SInclair ZX spectrum’s ROM for example had more than its fair share of bugs, and its BASIC programming experience with single keypress was unique but also slow to run. It’s something [Jonathan Cauldwell] has addressed with his Arcade Game Designer ROM, a complete and ready to run replacement for the original Spectrum ROM that contains a scripting language, a compiler, editors for in-game assets, and a game engine upon which to run your games. It’s the ROM you wanted back in 1983, when you were struggling to fit a bit of Z80 code in a Sinclair Basic REM statement.

If you’re a Spectrum enthusiast and think this sounds a little familiar then you are of course correct. It builds upon his past work with his Arcade Game Designer, with the distribution by ROM allowing the developer to use the full 48k available on all but a very few early 16k machines. You’ll need your own EPROM on which to burn it, but we suspect that if you’re the kind of person who has a Spectrum and has writing these games in mind, you already have access to the relevant equipment.

If you’re new to all this Spectrum stuff and where its ROM came from, then maybe it’s time for a trip down memory lane.

The ZX Microdrive: Budget Data Storage, 1980s Style

September 18, 2020 by Jenny List 53 Comments

An enduring memory for most who used the 8-bit home computers of the early 1980s is the use of cassette tapes for program storage. Only the extremely well-heeled could afford a disk drive, so if you didn’t fancy the idea of waiting an eternity for your code to load then you were out of luck. If you had a Sinclair Spectrum though, by 1983 you had another option in the form of the unique Sinclair ZX Microdrive.

This was a format developed in-house by Sinclair Research that was essentially a miniaturized version of the endless-loop tape carts which had appeared as 8-track Hi-Fi cartridges in the previous decade, and promised lightning fast load times of within a few seconds along with a relatively huge storage capacity of over 80 kB. Sinclair owners could take their place alongside the Big Boys of the home computer world, and they could do so without breaking the bank too much.

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3D On The ZX Spectrum 48K

August 17, 2020 by Inderpreet Singh 16 Comments

There are times when a project becomes such a big part of a maker’s life that they find themselves revisiting it even years later. [Thanassis] combined this phenomena with his love for the ZX Spectrum when he ported one of his old 3D rendering projects to the ZX Spectrum 48K. The video below shows the result, and they speak for themselves.

The roots of this project go back around three years, when [Thanassis] posted a similar project for the ATMega328 which employed fixed point math tricks for achieving the graphics. The code needed to be even tighter to run on the Spectrum, eventually getting boiled down to just a handful of calculations. This got the proof of concept working with the z88dk compiler, but it wasn’t quite fast enough.

In the end, hand assembly optimizations nearly doubled the performance to a blistering 10 frames per second. There’s also a version that kicks it all the way up to 40 FPS, but only if you give it a few minutes to do the calculations ahead of time. With a few teaks and the right display, this project could produce some very cool retro visuals.

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