INTERVIEW OF DEREK ANDREWS
programmer of LEAP-FROG and MUNCH AND CRUNCH
for the VOLTMACE DATABASE videogame system
did you come to work for Voltmace?
I had just been laid off by Texas Instruments (UK) when the job became
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
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
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
I developed a plug-in and software that enabled zx81 users to program
the database in machine code.
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
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
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
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
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
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.
Thanks to Michael Davidson and his website Obscure
Pixels for the screenshots.
about Voltmace Database and compatible systems
VC-4000 (compatible system) page