My Software

Games

Yes, I am the Andy Key who wrote all those old Memotech MTX games. Guilty as charged.

Here are some screenshots :-

These games (and games by others) are all bundled within, and can be played on, the MEMU Memotech Emulator.

I made a few hundred quid from royalties from these games. I used this money to fund bigger and better computers.

I also wrote a port of Blobbo for the Sinclair Spectrum :-

There were other games that were never finished :-

• I wrote a bit of a 3D isometric game, a bit like Sepulcri Scelerati by Chris Sawyer, for the Sinclair Spectrum. Looked good, but I just never got to finish it.
• I wrote half a 3D isometric game that looked a lot like Ant Attack, only on a much grander scale.
• I wrote the beginning of a smooth scrolling game, using some of the techniques in Surface Scanner, only with a aeroplane flying in the sky with clouds. Looked similar to Time Bandits, but it also scrolled smoothly vertically.
• I tried to write an Elite / Star Wars style game, using a Bresenham line drawing algorithm and matrix maths. It worked, at around 10 frames per second (the bare minimum for animation), but this wasn't enough to make the game viable.

Back in these days, computers were really slow and small. The amazing thing is that it was possible to write playable games. We used all sorts of devious tricks to fit them in, such as self-modifying code, initialisation code that was overwritten later with data, using the stack to move/copy data, precomputing everything and storing it in lookup-tables, etc...

If you could find a way to do something cool on the computer, then you probably had the kernel of a game. eg:

• if you could scroll the screen, you had a scramble variant - Mission Alphatron
• if you could scroll the screen smoothly, you had Surface Scanner
• if you could do table based lookup maths for sine, cosine and division, you could do 3D games such as Star Command.

Most games were written in 4 to 6 weeks, working most days. I didn't get out much as a kid.

Unfortunately, I've lost the source to the games. Occassionally I try to reverse engineer SMG2M a little further.

Here are the mazes for SMG2M - 1, 2, 3, 4, 5, 6.

My daughter and I reverse engineered the map to the Caves of the Orb, from the CP/M version. The cassette version with graphics is probably the same or similar.

Z ZX Spectrum Emulator

This is described here.

Military Training

A company in Rome saw SMG and approached me to write some MTX software for a product to be used to help train the Sicilian military! The MTX screen was attached to the sights of a real ground-to-air "turalite" (gun), and it would display a view of a missile flying through the sky, in a parabolic arc. Two soldiers, one controlling the side to side motion of the gun, the other controlling the elevation, would attempt to track the missile, by turning various dials, hopefully at the right relative speeds with respect to each other. My program would receive information regarding the position of the gun from registers on a bit of custom hardware, and would update the screen accordingly. Soldiers would be graded on how much of the time they managed to closely track the missile. As a school boy, I flew to Rome to complete this assignment, and for the week I was there, I had the top floor of a rather nice villa to myself. I became a millionaire as a result, and although it was only a million Lira, that was a lot of money for me at the time.

SDX with CP/M

I got hold of the source used in the FDX for the boot ROM, including the drivers for the keyboard and 80-column card. I replaced these drivers with my own which accessed the MTX keyboard and the MTX VDP chip (in a rather low graphic quality 56 column mode). I also got the source to the SIDISC.COM program, which installed CP/M support for Silicon Discs and RAM discs, and integrated this so it was a part of my new boot ROM. This ROM was known as the SCPM ROM, and has been mentioned above.

The result was a massively smaller and cheaper CP/M system running on a MTX512 with 3.5" SDX disk, and 512KB of RAM disk. I also changed to boot order to try the RAM disk (F:51), if it contained what looked like a valid copy of CP/M. Failing that, it wall fall back to booting from 3.5" disk (B:3). Once CP/M and other files were copied to the RAM disk, this system could boot CP/M in 2 seconds flat, and assemble and link code faster than an SM1.

I had to patch the Newword word processor to make it work properly on a 56 column screen (rather than 80), but once that was done, this platform was perfectly good enough for development work.

Memotech used this boot ROM commercially with their first generation of Video Wall products.

Then I wrote a program RCPMGEN.COM, which would read the RAM disk and create ROM images to burn EPROMs with. These ROMs would be used with a RSCPM boot ROM, which at boot time would copy the RAM disk images from ROM to RAM disk. The net effect was you could make a MTX512 with MTX ROM card and MTX RAM card and no floppy disk, which booted CP/M from ROM. This made use of a "sub-page" feature in later ROM cards whereby one of a number of 8KB pages could appear in a single ROM page slot, selected by writing to location 0 in memory.

Video Walls

Screenshot :-

After Memotech gave up selling home computers, it started designing, manufacturing and selling video walls.

I wrote the software to control these, which ran on CP/M on the SDX with my modified boot ROM. The video walls were controlled by sending command strings down the centronics printer ports. This allowed Memotech to use its stock of MTX kit as a part of its video wall offerings. I subsequently wrote better software which ran on MS/DOS on the IBM PC.

I still have the source to both the original MTX version and the later PC version of this. I even recently modified the PC version to work on modern PC hardware, which is massively faster than it was at the time.

On the MEMOTECH MTX Computersystem website is the "Cameron Video Wall Users Guide", which is a scan of the manual that was created for the video wall program. Cameron were a distributor for the video walls created by Memotech. I had no idea this manual had been created. I had thought it straightforward enough to use without one.

Kermit

I ported Kermit (a terminal emulator, communicating over RS232) to the MTX computer. This wasn't hard, the MTX used similar hardware to other Z80 CP/M based systems - it was just a matter of finding ports and memory addresses. This allowed me to transfer files between my MTX and my new PC.

Today I use MFLOPPY.