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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 7th Oct 2019, 3:02 pm   #1
TALKINGWITHPYE
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Default Dragon 32

Hello, I was looking through the postings of vintage computers but did not see any mention of the Dragon 32. That was my first computer, did anyone else use these machines. I managed to write a program for drawing circuit diagrams using BASIC.
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Old 7th Oct 2019, 3:19 pm   #2
RogerEvans
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Default Re: Dragon 32

Yes, I have fond memories of the Dragon 32, originally assembled a couple of miles from where I was brought up in Swansea. I bought it with the sole object of writing a flight simulator that could do full 3D aerobatics and eventually managed to write several kilobytes of machine code totally by hand without the benefit of an assembler. I found a PCB for add on EPROMS and put the flight simulator into an EPROM but copied into RAM on startup because there was some magic POKE that fiddled with the registers of the address multiplexer and ran code from RAM at double speed.

Happy days but I am afraid the Dragon 32 and all the notes on the flight simulator are long gone.

Roger
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Old 7th Oct 2019, 5:04 pm   #3
TonyDuell
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Default Re: Dragon 32

The Dragon 32 was based on a Motorola example circuit for the 6883 SAM (Synchronous Address Multiplexer) chip. The Tandy/Radio Shack TRS-80 Color Computer ('CoCo') was based on the same circuit. The ROMs were different (meaning tokenised BASIC programs for one would not load on the other) and the other main difference was the printer port.

Anyway, I have several CoCos with disk drives. OS-9 (not the Apple thing, the one from Microware) was a wonderful operating system, allowing multitasking and even multiuser operation.

I also have a CoCo3, a machine which had no Dragon equivalent. The SAM and VDG (6847 video chip) were replaced by a Tandy custom IC called GIME (Graphics, Interupts, Memory Enhancements) which gave an 80*24 text display with true lower case,640*200 graphics and a memory management circuit allowing up to 512K of RAM.

I don't know if I mentioned this before, but I really understood how to use that CoCo 3 (and other machines of a similar vintage) to do the things I wanted. I built interfaces, wrote device drivers, wrote simple application programs to do things like program EPROMs, convert data files, control lamps and motors and the like.

I can't figure out how to do that sort of thing on a modern computer. Sure it's a lot more powerful, but it's doing the things the manufacturers want. It is actually doing less _for me_.
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Old 7th Oct 2019, 6:03 pm   #4
Electronpusher0
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Default Re: Dragon 32

Many years ago I worked for ATE systems in Chichester (now defunct) and we were developing a cable harness tester for testing such things as Aircraft looms.
We based the computer control on the same Motorola applications note as the Dragon. We used Dragon 64s (same as the 32 but twice the memory) as test beds to develop the software.
The Dragon used a 6809 8/16 bit processor.
I spent some time de-compiling the code of the Dragon out of curiosity. It used a technique that we regarded as bad practice at that time - self modifying code.
Part of the code was held in Ram, loaded at boot. First time through that bit of code it did one thing, the code was then modified and subsequent passes through that bit of code did something completely different.

Peter
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Old 7th Oct 2019, 8:40 pm   #5
mark_in_manc
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Default Re: Dragon 32

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Originally Posted by RogerEvans View Post
...there was some magic POKE that fiddled with the registers of the address multiplexer and ran code from RAM at double speed.
They didn't all do that - mine just used to crash I taught myself basic on one as a teenager and got so far as implementing arrays in order to move user-defined graphic objects around the screen. Can you imagine how slowly it ran! Still, it was all great preparation for Fortran 77 at university - thanks Dad, it was a big family outlay at the time.
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Old 7th Oct 2019, 9:14 pm   #6
Richard
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Default Re: Dragon 32

I had one as my first computer, used it for years.
Tape recorder to load a few bought games, and managed to write a basic program to play Mastermind (working out colour of 4 hidden coloured pegs).

Poke &HFFD7,0 - this used to "up clock" it, this would run some programs quicker, but not all. It also made the cursor faster.

This was 40 years ago, and I still remember &HFFD7,0 …. but no idea what I did this morning, how is that?

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Old 8th Oct 2019, 9:40 am   #7
TALKINGWITHPYE
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Default Re: Dragon 32

Hello again, it is interesting to see your responses to my posting, every individual devises their own line of interest. I got a great deal of satisfaction out of my program and when I look back to the article I wrote for the Dragon User magazine and see the listing I am amazed that I did that.
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Old 9th Oct 2019, 4:59 pm   #8
electronicskip
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Default Re: Dragon 32

I have a Dragon 32 and a Dragon 64 in my possession although in all honesty ive never really used them that much .
I was at the Waterfront museum in Swansea yesterday and they had one on display there too.
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Old 9th Oct 2019, 6:15 pm   #9
Richard_FM
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Default Re: Dragon 32

I heard that the Dragons didn't support lower case letters as standard, which limited their educational use.
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Old 9th Oct 2019, 6:41 pm   #10
TonyDuell
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Default Re: Dragon 32

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Originally Posted by Richard_FM View Post
I heard that the Dragons didn't support lower case letters as standard, which limited their educational use.
Correct. It used the 6847 video chip which had an internal character generator ROM for upper case only.

I think one of the word processors for the Dragon used the highest resolution graphics mode and generated the characters in terms of the pixels in that mode, which allowed lower case. I never used that program though.

As I mentioned, the CoCo3 has true lower case in the hardware. But that machine was never sold in the UK. Most outputted NTSC video at US TV rates. According to the service manual there was a PAL version, sold in Australia?, but I've never see it.
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Old 9th Oct 2019, 10:27 pm   #11
SiriusHardware
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Default Re: Dragon 32

There was a 'Dragon Meet' at the Centre For Computing history (Cambridge) in July '19 - I didn't go as my interest in these machines is peripheral, but I got the impression it was a regular event, not sure of the interval between meetings. Might be worth seeking out if you are a fan.
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Old 10th Oct 2019, 7:29 am   #12
Electronpusher0
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Default Re: Dragon 32

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Originally Posted by SiriusHardware View Post
There was a 'Dragon Meet' at the Centre For Computing history (Cambridge) in July '19 - I didn't go as my interest in these machines is peripheral, but I got the impression it was a regular event, not sure of the interval between meetings. Might be worth seeking out if you are a fan.
That's where my Dragon 64 went. I donated it to the centre when we moved.

Peter
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Old 10th Oct 2019, 11:58 am   #13
dominicbeesley
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Default Re: Dragon 32

I'm a relatively recent 6809 convert - I never owned a Dragon but a friend did at school. I think the 6847 really let it down as with the blocky uppercase type and funky disco-era colours it seemed quite dated against the Spectrum and BBC - well to a 9 year old me it did.

If I'd been my age in the 80's I'd have chosen it over the Spectrum any day if not the Beeb!

D
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Old 10th Oct 2019, 12:57 pm   #14
SiriusHardware
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Default Re: Dragon 32

The thing I noticed most about TCFCH is their remarkably brave / bold decision to put almost all of their classic 80s computers within reach and powered up.

They must have a mountain of spares, as I imagine they must have quite a high rate of attrition. I appreciated it though, I spent time playing with several machine, including a Dragon and a Sinclair QL, that I have never laid hands on before.

The National Museum Of Computing offers a similar experience but only with a room full of BBC Bs, which of course were pretty tough, well made machines.
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