Eddie's Micro page.
Some recent micro projects can be found on my projects page

This is a photo of my first computer

I built this Mini-Scamp microcomputer in 1976 (I think). It was a Dick Smith Electronics (DSE) kit from the days when Dick Smith actually owned and ran Dick Smith electronics. The design was published in "Electronics Australia" (EA). It was based on the SC/MP CPU from National Semiconductors. It boasted a massive 256 bytes of RAM (yes Bytes not Kbytes) - this was 4 times more than the earlier model. It had no ROM or EEPROM of any kind. The complete user inferface is visible in the photo above. Binary code was entered into the RAM by dialing up the data byte and address in binary using toggle switches. Pressing the deposit button stored the byte in memory. The LEDs showed the current contents of the memory location. After the program was enter in this manner one of the switches on the right was flipped from DMA to run mode and the micro executed the code (the other switch was power). The micro could display bytes on the LEDs and read bytes from the data switches - the request LED was there to signal the user to enter a byte and press deposit. No problem with Y2K bugs, viruses or hackers here.
I almost built a EDUC-8 - a computer that didn't use a micro-processor, you built the processor out of logic chips. There are still people around who get a kick out of this sort of thing - and amateurs who design and build there own processors as I hope to discuss later in this page.
I did not manage to do much with the SCMP, it played a few tunes out of the speaker I added and it flashed random numbers on it's LED display - but it was a good start into the world of micro-computers.....

The 2650 - 1979

After the SCMP came the sygnetics 2650. I stayed with this processor for many years and many generations of hardware. My first 2650 was another kit probably EA and DSE as above. From memory it had up to 7K of RAM and 1 K of rom. It ran from a 110 baud serial key board, talked to a 110 baud serial video terminal unit (VDU) and could load and save programs onto a cassette again at 110 baud. Compared to the SCMP this was heaven. The keyboard VDU and cassette were all kit built and I used a large valve TV for the display.
Then it started to grow. The EA cpu card was replaced by a KT9500 card and then by an S100 based card.
The serial VDU was replace with a memory mapped VDU (that could do chunky graphics). The cassette system was replace by a homebrew "non return to zero" (NRZ) interface and a homebrew tape file format. The NRZ interface used software driven phase encoding (aka Manchester encoding). Western digitial released a single chip floppy disk controller (wd-1770??) and a (now) friend of mine Mike Van Emmerik and a friend of his (Ron Harris) designed a floppy disk inferface and a DOS for the 2650. I wire wrapped a controller borrowed money off my mother to buy a drive (around $600 for a 100K floppy drive) and out went the tape. The floppy controller was single denisty (for those who still know what that means). Around 1982 WD released a double density controller (3 chip set), now it was my turn to design a controller card - and this was it.

Double density, 8 and 5 inch floppy disk controller with EPROM programmer and real time clock. - 1982

I had you do some major work on the DOS to get it to work with this card. The CPU only ran at 1 megaherz and wasn't fast enough to pole the controller as it did previously this was because of the higher transfer rates for double density and/or 8 inch drives. There were other problems as well while formating the longer tracks.
My first printer was a baudot printer. The type the post office used for sending telegrams. It weighed slightly less than I did and the whole house shook we it printed. Baudot code was a 5 bit code send at 50 baud - it would print around 5 cps. I had a number of printers over the years including a Burrows Teller terminal I hacked into.

One of the programs I wrote when I first got a VDU that could do crude graphics was a game I called UFO - very crude - it was around 1979. Anyhow I got this email a few months back...

Reply-To: "Andrew Davie" <adavie@mad.scientist.com>
From: "Andrew Davie" <adavie@mad.scientist.com>
To: <eddiema@ozemail.com.au>
Subject: 2650 UFO Date: Wed, 11 Mar 1998 22:29:05 +1100

"...every few seconds a UFO will traverse the screen, on the base line is drawn the lid of a missile silo" I have a listing in front of me, circa 1979 and written by E.Matejowsky. I'm figuring thats you, and thought you'd get a kick out of learning someone nearly 20 years later is casually browsing through the listing. Cheers A

I'm a collector of old computers - anything homebrew or early home and game computers (not IBM!!) and this is one of the ways I build up contacts and track down old machines, programs and documentation. This listing was saved from the dumpster some number of years ago by an electronics guy, and when he decided to sell his old computer (to me!!), I asked if there was anything of this sort he would like to send to a good home. Having found the listing I thought it would be both fun and possibly productive attempting to find the original authors of some of these programs. I'm persistant like that ;) So, a few net searches (just a couple of minutes actually - I wish I could make it sound more sherlock-holmesish but it was simple) and I found you :)

Of course, your name wasn't that hard to track down - but I've also found some of the other authors of these programs, too. The reactions have been fun, including "well bugger me dead!!"

Cheers A

Until 1982 virtually all the programming I did was in assembler. I got interested in a language called FORTH after spending some time on Great Keppel Island with Peter Milford and his friends who were forth fanatics. Later I was given a FORTH compiler for the 2650 by a friend -the late Dr Dan Hamilton and slowly got to understand this odd language. Around this time I resigned from my job in the photographic industry and tried to make a living amongst other things by fixed video games, unfortunately I didn't see the money for much of what I did and needed to find something else.
Another friend, Ed Hancock suggested I design a boat alarm and I did so. I figured the 2650 was too expensive @ $25 each and instead used a 6502 @ $5. I wrote a conventional 2 pass 6502 cross assembler in 2650 forth and programmed the 2K eproms for the alarm in the card show above. Needless to say it flopped we sold a grand total of one. We called the system Compu-guard. Around this time I met a guy named Terry Ryan who was Oz inventor of the year for his prop-scan propellor pitch measuring device. I wrote some code for him for a navy contract he had (sort of). He had a dream of setting up an innovations centre on the Gold Coast. This would have been great but Dan found me a job at the University of Queensland and I didn't get involved with the proposed centre.- a pity you can't do everything.

My time at
UQ – 1984-1992
Home Office- 2003 ????

External link

Great Microprocessors of the Past and Present

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