Dragon 32/64

From Academic Kids

The Dragon 32 and Dragon 64 were home computers built in the 1980s. The Dragons were very similar to the TRS-80 Color Computer, and were produced for the European market by Dragon Data, Ltd., in Port Talbot, Wales. The model numbers reflect the primary difference between the two machines, which had 32 and 64 kilobytes of RAM, respectively.

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Dragon_32_computer.jpg
A Dragon 32 Home Computer
Contents

History

In the early 1980s, the British home computer market was booming. New machines were released almost monthly. In August 1982, Dragon Data joined the fray with the Dragon 32; the Dragon 64 followed a year later.

In the private home computer market, where games were a significant driver, the Dragon suffered due to its graphical capabilities, which were inferior to other machines such as the Sinclair ZX Spectrum and Commodore 64.

The Dragon was also unable to display lower-case letters easily. Some more sophisticated applications synthesised them using high-resolution graphics modes (in the same way that user-defined characters would be designed for purely graphical applications such as games). Simpler programs just managed without lower case. This effectively locked it out of the then-blooming educational market, which came to be dominated by the Acorn-built BBC Micro.

As a result of these limitations, the Dragon was not a commercial success, and Dragon Data collapsed in June 1984.

Despite the demise of the parent company, Dragons still proved quite popular. They had a robust motherboard in a spacious case, and were much more tolerant of home-modification than many of their contemporaries, which often had their components crammed into the smallest possible space.

Technical notes

The Dragon was built around the Motorola MC6809E processor running at 0.89 MHz. For the time, this was a relatively sophisticated 8-bit CPU, with limited 16-bit capabilities. In terms of raw computational power, the Dragon beat most of its contemporary rivals (which were based on the older MOS Technology 6502 and Zilog Z80) but this made little difference in a market where graphical capabilities were much more important to consumers.

Numerous peripherals existed for the Dragon 32/64, and on top of this there were add-ons such as the Dragon's Claw which gave the Dragons access to the BBC Micro's large range of accessories (a particularly important factor in the UK home market). Although neither machine had a built-in disk operating system (cassette tapes being the default data-storage mechanism in the home computer market at the time) DragonDOS was supplied as part of the disk controller interface from Dragon Data Ltd. In addition to the DragonDOS operating system the Dragon 32/64 were capable of running several others, including FLEX and OS-9 which brought UNIX-like multitasking to the platform.

Many 32s were upgraded by their owners to 64K. A few were further expanded to 128K, 256K, or 512K, with home-built memory controllers/memory management units (MMUs), and were able to run OS-9 Level 2. The numerous external ports (by the standards of the time) including the standard RS-232 on the 64 also allowed hobbyists to attach a diverse range of equipment.

Differences from the TRS-80 Color Computer

Both the Dragon and the TRS-80 Coco were based on a Motorola data sheet design for the MC6883 SAM chip for memory management and peripheral control.

The systems were sufficiently similar that a significant fraction of the compiled software produced for one machine would happily run on the other. Software running via the built-in Basic interpreters also had a high level of compatibility, but only after they were re-tokenized (which could be achieved fairly easily by transferring via cassette tape with appropriate options).

The Dragon had additional circuitry to make the MC6847 VDG compatible with european 625-line television standards, rather than the US 525-line NTSC standard, and a Centronics parallel printer port not present on the Coco. Some models were manufactured with NTSC video for the US market.

Differences between the Dragon 32 and Dragon 64

Aside from the amount of RAM, the 64 also had an RS-232 serial port which was not included on the 32.

A minor difference between the two Dragon models was the outer case color; the Dragon 32 was beige and the 64 was light grey. Besides the color and the Dragon 64's serial port (and the model name stickers, of course), the two machines looked exactly the same.

Dragon trivia

  • Accessing certain memory mapped control registers let the processor double its ROM and/or RAM access speed. Unfortunately, the latter somewhat compromised the stability of the system.

References

  • Vander Reyden, John (1983). Dragon 32 programmer's reference guide. Melbourne House. ISBN 0-86161-134-9.
  • Smeed D & Sommerville I Inside the Dragon Addison-Wesley, 1983

External links

  • The Dragon 32/64 Computers (http://www.6809.org.uk/dragon/) – at website www.6809.org.uk
  • Dragon Information Files (http://www.grempc.demon.co.uk/dragon/info/) – from Graham's Dragon Page, by Graham E. Kinns
  • The Dragon Archive (http://www.dragon-archive-online.co.uk/) – An archive of everything related to the Dragon 32/64 and its clones and prototypes
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