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Untitled Document

INTERVIEW OF DEREK ANDREWS
programmer of LEAP-FROG and MUNCH AND CRUNCH
for the VOLTMACE DATABASE videogame system

 

Munch & CrunchHow did you come to work for Voltmace?

I had just been laid off by Texas Instruments (UK) when the job became available.

Where were you based by the way ?

Texas Instuments in Bedford, Voltmace in Baldock.

Did you program other games before and after? for other systems?

No. I didn't even have a particular interest in games. I think it was my enthusiasm for meeting the technical challenges that got me the job. I had done a little Fortran programming at school, another high level language at university (I think it was Cobol) and my final year project was based on a 6800 processor. While at TI I programmed their ATE for memory chips.

Were Leap Frog and Munch & Crunch the only games you programmed for the Voltmace database? even prototypes?

I worked on a version of Defender, but don't recall whether it went into production.

Was it that game ? http://www.dieterkoenig.at/ccc/it/s_it_games_40.htm

Same idea, but not that version. As I recall it had a 'radar' area underneath the main play area showing more distant enemy vessels.

What else did you do ?

I did a little harware design on joysticks, taking the Database bodies and adding electronics to make them compatible with other home computers.

That is to say ? Were they analog or digital by the way?

They were analog, which of course means more flexibility in terms of being able to control direction (full 360 degrees rather than just 8 ways) and speed. The keypad was also a bonus. The hardware (electronics) was mainly just interfaces for various computers, but again I really can't remember the details. I think one of them was pulse width modulated and required a monostable chip. I think the the biggest seller was for the BBC microcomputer.

I developed a plug-in and software that enabled zx81 users to program the database in machine code.

With a cable going from the expansion port of the ZX-81 to the cartridge slot of the Database?
Could you program directly the Database this way ?
Did this was ever produced? Marketed ?
Was it used by other people than you?
Do you remember examples made with this addon?

The interface was built into a cartridge which had a cable going to zx81 expansion port. The cartridge had a RAM inside which could be accessed by either the database or the zx81. The development process was extremely crude, and required the user to write assembly code on paper, convert it manually to machine code, and type it into the ZX81. The ram would then be switched to the database which could execute the program. Very crude, but the only affordable way for home programmers to be able to design real time games with good graphics and speed. In those days, home computers had very rudimentary graphics capability. This allowed access to the power (haha!) of a graphics chip designed for games rather than text. I would be very surprised if anyone actually had the patience to design more than the most rudimentary game with it. I think we sold only one or two of those systems.

I also did some design work for an add on to the Memotech home computer, basically adding an analog port for joysticks.

Are you talking about the MTX computers?
Did you work for Memotech too ?

Thats the one. I actually owned one of those for a while, but I didn't have any association with Memotech.

Were you or Voltmace not upset about legal rights for these games (Pac-Man / Frogger)?

My name never appeared on the games:) I don't know the legal issues, but presumably only the name can be protected. I left all that to management to worry about.

How did you learn Signetics 2650 assembly language?

From the data sheet. As I recall it is quite similar to 6502 in its structure. The biggest hurdle was the graphics chip which was very limited in its capabilities. It only had four sprites to play with and if you needed more they had to be reprogrammed on the fly. Good use of the interrupt system is an important part of programming this system.

Were these data sheets given to you by Voltmace? Signetics?

I was given them by Voltmace. I don't know how they came by them, but presumably the manufacturer. I found the comments about the military uses of the processor quite interesting. I would be very surprised if they designed the architecture of the processor on a speculative basis just for the military. Plus, why would they design a games chip to go with it?

Military semiconductors are usually just commercial chips, in a ceramic package (better hermeticity and thermal characteristics) which are then electrically and environmentally tested to rigorous standards (often -55C to +125C), along with destructive tests on a sampling basis. But functionally there is not usually anything very special about them. I certainly doubt that the 2650 had any classified functionality! (PS I was test engineer for 'military' MOS memory at TI)

Did you also have the 2636 datasheets?

Yes. They were as important as the processor! Understanding that chip and figuring out how to make it dance was key. I found a reference on a bulletin board about this chip, and someone had posted a plie of information about it. But you might be able to get data sheets from Signetics if you ask nice!

LeapfrogWould it happen that you still have some of this stuff?

I don't think so. I probably left everything behind at Voltmace, and have moved house and emigrated since then, so it is unlikely that I still have anything.

What hardware did you use to developp the games?

A CPM based system that saved the assembly code to disk and blew machine code into EPROM.

Do you remember wich model/system?
So you had to burn the EPROM each time you wanted to test something?
You didn't have any kind of emulator?

It was a system made specially for Voltmace by a computer consultancy. The development system had a shared RAM which could be read from the Database. Certainly there was no emulator or debugger. It was really not much more than a text editor and assembler.

I remember doing a lot of work with an oscilloscope checking to see how long various bits of code took to run to make sure all the graphics handling were operating fast enough.

I was surprised to learn that Signetics had a development system for this processor. I certainly didn't know anyone ever wrote a book about it!

Did you know other Voltmace database programmers?

There weren't any others. My boss, Tony Pearmain, had a rudimentary understanding of the technicalities.

Do you know from who Voltmace licenced the hardware? Was it from Interton? from Signetics/Philips?
Do you know anything about related systems such as Emerson Arcadia 2001, Interton VC-4000, Hanimex 2650, etc. ?

The rest of your questions I really can't answer. All I remember is that Voltmace bought the design from another company. They improved the quality of the boards and video. The mouldings may also have been new, but again I don't remember. At the time it was just an obscure system that I had to figure out how to use.

So all other Voltmace games were licenced ones?

I couldn't say how the licensing of the harware or software was done.

Sorry to take so much of your time, but your memories would be very interesting for a lot of people, and of understand the history of these obscure systems...

I was amazed to find it mentioned on the web, let alone find so much interest in all these old games. I never knew I was making history during my time at Voltmace.

Related links:
Thanks to Michael Davidson and his website Obscure Pixels for the screenshots.
Article about Voltmace Database and compatible systems
Interton VC-4000 (compatible system) page



  
       
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