News, Reviews and Letters Index > Street Life Column From PCW 16 Sept, 1982

Jupiter Ace -
the making
of a micro

David Kelly returns to
Foxhollow in pursuit of the
Jupiter Ace

Now the Jupiter Ace has arrived (Popular Computing Weekly, September 9) the tongues of Altwasser and Vickers have beer untied and they can talk about their new micro, the machine that is not afraid to speak Forth.
  The two co-designers of the Spectrum left Sinclair five months ago to develop the machine.
  "I first thought in November last year that it would be a good idea to build a microcomputer," says Richard.
  "I knew that I couldn't do the whole thing on my own. I can't write machine code —at least, I can't write it like Steve can.
  "I turned the idea over for some time but it wasn't until January that I mentioned anything to Steve.
  "I didn't know how Steve would feel about setting up on his own. I had always thought Steve was a fairly cautious sort of chap and I wasn't sure if he would be interested."
  "As we talked it became clear that Steve was prepared to be adventurous — and it became clear to him that I was prepared to be adventurous — and there you are."
  Both Richard and Steve wanted to do something different, so they decided that their micro should run Forth rather than Basic.
  "We'd been talking before Christmas about Forth," explained Richard. "We had both independently read an article that was printed in the magazine Byte — and we both got quite excited about it".
  Having decided to build a new micro that would run Forth, the two designers began to sort out the details of the new machine.
  "We spent the last weekend in January sitting down trying to work out the basics of the Ace. We both know the Z80 processor inside out so we really had to use it, and at that stage I already had an architecture in mind.
  "The Ace had to be fairly inexpensive for two reasons. You can always make a small computer bigger by hanging a selection of peripherals on it — which makes the small micro a better commercial proposition. And we obviously know so much more about making small computers.
  "We agreed to spend a month evaluating the project. We both joined FIG, the Forth Interest Group. Steve went off and bought

Steve Vickers (left) and Richard Altwasser, co-designers of the Jupiter Ace.
lots of books and I started making enquiries of component manufacturers."
  "We agreed to spend a month evaluating the project. We both joined FIG, the Forth Interest Group. Steve went off and bought lots of books and I started making enquiries of component manufacturers."
  By mid-March they were still not making much progress and they realised that, if they were going to see the venture through, they would have to leave Sinclair. There was only one time to do that —immediately after the Spectrum launch.
  "We couldn't possibly leave before, and, if we waited long after we would more than likely be headlong into another of Clive's projects," says Richard. "So we left and went headlong into one of our projects instead."
  By this time the first draft of the hardware was already working.
  "If you look at all the new computers coming out they all have new hardware —ours was to have entirely new software as well. Writing the Forth was a huge task for Steve.
  "While he was doing that I redrafted the hardware, and designed the printed-circuit board. Mixed in with this I was sorting all the components — looking around the factories for someone to build it. We also approached the bank to try to get a three-month loan.
  "Forth is a very well documented language. We decided on Forth 79 Standard, with some modification, and Steve built it all up from scratch.
  "To say Basic is becoming the standard language for micros is very misleading — you show me two machines that run the same version of Basic. Forth is a better language. It is about ten times faster than Basic. It is more compact — we could easily do a 1K Space Invaders in Forth on the Ace.
  "Forth is easier to learn, as the first language. Changing from Basic to Forth
is a bit like going on the continent and driving on the right: You quickly get into the way of it, but in the first 20 minutes you risk your life so many times."
  The Jupiter Ace will get its full launch at the Personal Computer World Show when the first production run machines will be on display.
  "We will build and ship 500 computers in September which will get us off the ground — production will ramp up from there according to demand.
  "In addition we are going to provide a memory expansion, although with a little adaptation any Z80 peripheral can be connected because all the Z80 busses appear at the back of the Ace.
  "We will be writing our own software for the machine and we are working closely with several companies who have written good things for the ZX81 and have expressed a wish to write for us.
  "Most people buy a micro to learn about computers. They spend a week getting into Basic and discover they cannot produce the kind of games they are used to without learning to program in machine-code.
That isn't easy so they resort to buying ready-made machine-code games. The manufacturer is selling a Basic machine to run machine-code. What the Ace does is to provide machine-code speed in an easily understood language.
  "Learning to program should be easy. If you buy a car it should be as easy to drive as possible. Why should a computer be different? It is the job of designers to produce machines that my grandmother would find easy to use.
  "I think," says Richard, "that the introduction of Forth is a major step in that direction. We know we are right to produce the Ace — all we have to do is convince everyone else of that."