Interview with John Hollis
January 1998


How did you get started in computers?

I played with electronics when I was a kid. At about 12 I started fooling with NAND gates and built a simple ALU. When microprocessors came out I moved jobs to a microcomputer outfit. I met a couple of experienced programmers while I was there: An American named Rick Smets who designed most of their hardware and wrote the OS (and the first PL/1 compiler on a micro), and a belligerent ex-Univac chap named Jorgen Karlsen who taught me how big programs are utterly different from small ones.

When did you first see a Spectrum and what were your first impressions?

At a ZX microfair. In those days QS sold add-ons for the ZX81 that included a high-res graphics board I designed. The Spectrum effectively duplicated our hardware add-ons so we dropped hardware to concentrate on writing games.

What was your first game?

Asteroids for the ZX81. Intruders for the Spectrum.

What have you done on the Speccy?

Intruders - a version of Space Invaders
Meteor Storm - a version of Asteroids with the first (awful) speech on the speccy
TimeGate - first (only?) 3D starfield on the spectrum
Aquaplane - Water Ski game with sharks
Games Designer - do it yourself instant game kit.

What do you think of your games? Which is your personal favourite?

Games designer was the most technically accomplished, TimeGate made the most money, but my personal favourite is Aquaplane.

How did you how did you do the border effect in Aquaplane?

1. Trap the frame interrupt by switching the Z80 to vectored mode and filling half a K of RAM with the same vector. ;-)

In the interrupt routine:
2. Set the border colour to cyan.
3. Scroll the clouds and horizon using constant-execution-time code.
4. Pad with a few nops then set the border colour to blue.
5. Service the virtual sound chip code.
6. Jump back through the ROM's original interrupt vector.

How did you sample the speech for Meteor Storm?

I used the cassette deck as a pre-amp and sampled a 1 bit stream into the mic socket using delta-time coding.

How did you leave the Spectrum scene? Were you sad to leave?

Nick Lambert and I thought that too many companies were entering the market, which in any case was saturating. Plus the fun was going out of it as it turned into a serious business. We sold the company for a substantial sum and I certainly have no regrets about it.

What are you doing now?

Programming and writing music. I still design games but I also write business software. All for the PC now.

What were the best/worse things about the Speccy?

Great cassette interface - best in the world. Hardware reliability was a bit of an issue - we used to buy them in quantity so there were spares.

What were your favourite Speccy games and why?

Ant Attack. Why? Utterly original. I wish I had written it!

Favourite Speccy coders/artists/musicians?

Sandy White and the guy who wrote the Picturesque assembler.

Do you use an emulator to play your old games (or any others)?

Not me. I still have a Spectrum or two.

What was the last Speccy game you wrote? Did you leave anything unfinished? (and if so is there any chance we'll ever get to see it!)

Game Designer was the last one published.

A horizontal scroller I was writing got shelved but I don't have the sources now.

Don't you ever feel like writing another Speccy game nowadays just for old times sake? ;-)

I hadn't until you mentioned it. I guess I would need a copy of the Picturesque assembler. And some time.

What do you think about modern games? Can they compete with the classics? Aren't they all presentation and no gameplay?

Some are excellent. ID software have done a brilliant job and produce some of the finest modern 3D games. It would be nice to see more originals. Some publishers seem to have got locked into trying to copy the most recent success of their competitors.

Is there anything you miss about the old days?

It was neat being able to create a new game single handed in a couple of months. It's usually six or more people and around 12 to 18 months now. I found it more challenging coding games on the bare metal and really pushing the hardware.

Any amusing anecdotes/stories etc about the old days?

I built a hardware mock-up to write our first Spectrum games, so we had working code before the first machines were delivered. We managed to get one of the first available (I believe the original batch was 2000 machines). I loaded the first game and for a brief moment there were rows of little space invaders and then it promptly crashed. After a few code checks I decided to test the hardware. Putting a C9 (return instruction) in RAM and calling it repeatedly would crash the machine! I whipped the oscilloscope out and checked; sure enough, they had the RAM timing wrong.

On the Z80 CPU a read during an opcode fetch is a bit shorter than a normal memory read. As the only executed code was running from ROM the problem would not have shown up. We told Sinclair. They recalled the machines. If you look inside an early machine you will see a transistor botched onto an LSI chip to fix it.

Have you anything to say to people who still use the Speccy today?

Have fun! I certainly did.


Thanks to John for doing the interview.

You can visit John's site.

Interview composed, conducted and edited by Philip Bee.