Steve Wozniak
Steve Wozniak
Written by Historian   
Wednesday, 11 August 2010

As co-designer of the Apple computer, Woz is one of the computer pioneers who have changed the way we work and play. But he was also something much rarer today, an electronics genius.



The computer business is just that - a business - and the history that it writes for itself often remembers the entrepreneurs first and foremost - the technicians are nearly always forgotten. If you discover or invent something really new then the academic history will take care of you but if you simply design something really well your place in posterity is far from guaranteed. We all know how important the Apple II was in the development of the personal computer but - who created it? You probably think that it was something to do with the famous Steve Jobs and indeed it was, but it was much more to do with a lesser known Steve - Steve Wozniak. This is the story of the Apple II, an important machine, but it is also the story of Woz.



Steve Wozniak

born 11 August 1950, San Jose, CA

Steve Wozniak was the son of a Lockheed engineer with a Caltech degree who designed satellites for a living. Electronics seemed to be a natural interest and Woz took to it enthusiastically. He read all he could find on the subject and designed and built his own electronics designs from an early age. A science fair project that he completed was a simple computer - it won. He was already fascinated by computers, even though the components he needed to build one cost far more than he could afford. It was in these early days that he met Steve Jobs via a mutual friend, Bill Fernandez. All three were interested in electronics but Woz, being five years older and with a natural gift for the subject, was the mentor and teacher.



Steve Jobs (left) and Woz (right)


Woz studied computer science for three years, the last year at Berkeley. While he was there his ability to design elegant and intricate circuits became clear. Phone Phreaking was the current fashion and Woz became intoxicated with the power of being able to phone anyone anywhere. He designed a "blue box", a multi-tone frequency generator that used fewer and cheaper chips than anyone else. Of course Steve Jobs got in on the act and arranged to manufacture and sell the devices - what a combination!

He planned to take a year off to earn money working as a technician at Hewlett-Packard but things didn't work out quite as he imagined. The distance was too far to commute back to Berkeley and studying at the local university would have involved starting over again. Anyway he was having far too much fun at HP to give it up and go back to Berkeley just yet. For the next three years during the day he worked on chip layout and in the evenings he became an electronic hobbyist. Back in Berkeley he had been keen on designing computers. He had designed over 50 different machines - but only on paper. Resources were so limited that even the output from the machines he designed had to be displayed on standard oscilloscopes rather than special purpose monitors. 

Woz first encountered the start of the microcomputer age when he saw one of Nolan Bushnell's Pong games at a bowling alley. A lesser man than Woz might have become hooked on the game - but not Woz. He became hooked on the game's innards - he built his own version of the game. Later Steve Jobs persuaded him to build a hard wired implementation of the "breakout" game for Atari. Nolan Bushnell was getting worried about the 150 plus chip count that most new games involved and he had heard of Woz's ability to design clever low chip count circuits - his pong used only 30 chips. The deal was that a design with 50 chips would earn $750 and under 40 chips would earn $1000. Woz's first design used 44 chips and he was so tired, the complete design had to be complete in four days, that it stayed above the magic 40 count and they only got the $750. This anecdote fails to convey the amazing achievement of getting a complex video game design down to 44 chips at all. A less inspired designer would have needed double that count!




Then came the personal computer. The Altair made the cover of Popular Electronics and Woz was one of the first 32 members of the Homebrew computer club. Components were now almost cheap enough for him to realise his dream of designing, building and owning a computer. He had already built a TV terminal based on a design by Don Lancaster, a similar spirit to Woz who never had the good fortune to bump into a Steve Jobs! From a TV terminal it would be a shortish step to a complete home computer - if only he could find a processor that was cheap enough. The 6800 he preferred was too expensive so a $25 6502 was the only possibility. Woz bought a 6502 and started his design.

Rather than follow the low cost per chip/high chip count approach, Woz decided that the fewer chips the better but the main problem was memory. At the time video displays used shift registers to hold the video data which was shifted out at video speeds but each screen location could only be updated once per frame, i.e. one character every 1/50th of a second or so. Woz wanted something faster because he had in mind writing programs to implement the sort of video games he had designed for Atari. A faster video design implied using RAM rather than shift registers but at the time the standard RAM chip only provided 1024 Bytes of storage. Steve Jobs suggested to Woz that he looked at the new 16-pin dynamic RAMs that were just beginning to become available.

Dynamic RAM is more difficult to design with and at the time making it work at all was considered to be the height of sophisticated digital design. Woz liked the idea because, although it was more complicated, it reduced the chip count to only 8 chips per 16KBytes. Other people were designing with dynamic RAMs but they were concentrating on providing memory boards for modular S100 type machines. Woz was designing a complete computer on a single circuit board and this was a very different way of thinking.
In the end he managed to get the whole lot onto a single board, six inches by eight using only 30 or 40 chips. The Apple I, as it came to be known was poor by today's standards but it was a complete computer and for the time it was a breakthrough. It used a 6502 processor, had 8KBytes of RAM and could run a simple BASIC in 4KBytes. It needed a keyboard, a monitor and two transformers for 5V and 12V. It had no speaker, no graphics and no colour. Its one expansion connector was used for a cassette interface. BASIC had to be loaded from tape and before that by hand because only a 256 Byte PROM was included with only memory load and examine functions. Steve Jobs and Woz sold around 200 Apple Is and out of this grew the entire Apple empire - but the next step was the Apple II.

Woz realised that the compact single board design had a lot of advantages but now he needed to add colour. The S100 modular machines of the time were just beginning to use colour displays but they were expensive. Woz had designed a seven chip colour circuit that would work with a colour TV. He also knew that domestic TVs were very sloppy in terms of their timing so he managed to produce a very low chip count 40 character display that didn't quite meet the TV standards specification but would work in most cases. He also cheated on the addressing for the memory mapped graphics to save two chips at the cost of a strangely mangled memory layout. For years to come users of the Apple II would wonder why memory adjacent memory locations didn't always control adjacent screen locations. A similar trick but this time adding two chips allowed him to shift out the memory locations directly into the video generator and so produce high resolution colour graphics. If you're impressed by the attention to detail the amazing fact is that Woz also wrote the system software including Apple Integer Basic - yes that's right they didn't need Bill Gates and Microsoft.

Even the prototype Apple II was impressive but Woz still wasn't happy. He wanted to play breakout, the game he had implemented for Atari - so he added a pair of game paddles. No he didn't bother with an AtoD converter, that would have been expensive. Instead he used a chip containing four (555) timers and used the paddles to control the width of the pulse that they produced - a habit that the IBM PC was to catch some years later. With this addition breakout was not only possible but relatively easy using BASIC. When enthusiasts were shown the machine they were more than impressed - they wanted one.

An odd feature of the design was the provision of expansion slots. These looked superficially like a bus but instead each slot had a pre-decoded memory location and the ability to include a 256Byte PROM and a 2KByte memory space. This allowed Apple II expansion cards to be simple because they didn't need to include their own memory decoding. This wasn't a completely new feature, for example the South West Technical Products (SWTP)  6800 machine used the same idea, but it helped make the Apple II great.


Apple I

A lasting design

Although the Apple II was an excellent design, I personally think that Woz reached a new height in the design of the Apple II disk drive. Every other manufacturer was building machines based on complex read/write electronics on the disk drive and then even more complex disk controllers in the machine. Woz didn't really know how disk drives were supposed to work and so he invented his own way of doing things. He started with a disk drive with virtually no electronics and then implemented an integrated controller and read/write electronics. The bulk of the work though was done in software and this simplified the electronics to an extent that, at the time, was difficult to believe. The Woz disk drive must have made a great deal of money for Apple because it cost next to nothing to make but sold for the price that users expected to pay for a disk drive! The Woz design was so clever that it lived on in and improved form in the Mac. The IWM, the Integrated Woz Machine, was a custom chip implementation of the same ideas.

Woz as "Rocky Clark"

In 1981 Woz was involved in a plane crash. He suffered head injuries and lost his ability to form new long term memories. He went to parties, escaped from hospital, played computer games and couldn't remember any of it. He eventually recovered but didn't go back to working at Apple. The accident was more an excuse than a reason for leaving Apple. By this time the managers had taken over and Woz was only a humble engineer. He left Apple and decided to go back to school! He enrolled at Berkeley again using an assumed name - Rocky Clark. Obviously a man a talented as Woz couldn't take the inanities of his lecturers without an argument - but who was "Rocky Clark" to tell them how to do it properly!

He returned to Apple at the end of the year but, apart from writing and giving away a spreadsheet that would have challenged VisiCalc if Apple hadn't killed it, he didn't do very much that was important. Back in the early days Woz could do magic things by saving a few chips and building really clever electronics. As the ability to integrate more into a single chip grew no one cared about clever design or saving components. This is the hardware analogy of the clever code that Bill Gates excelled at in the early days.You could look at a Woz design and spend hours wondering what any given component was doing - the answer was that it usually was doing more than one job! The growth in the power of hardware, mainly the low cost of large amounts of memory, removed the need for that skill as well! Only one other designer has shown the same skills as Woz and that's Clive Sinclair. The age of the clever elegant economical design, be it hardware or software, seems long gone.

For an account of Woz's life in the decade or more after this article was originally written see his 2006 autobiography,  iWoz:From Computer Geek to Cult Icon: How I invented the Personal Computer, Founded Apple and Had Fun Doing It, co-authored with journalist Gina Smith.



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