[Coco] HD63B09EP on ebay

[Richard Atkinson]

Hi Mike,

The Dragon 32/64 is sufficiently different from the CoCo to make
hardware conversion a fairly involved business. For the most part the
computers contain equivalent interfaces that work the same way, just using
different pins on the PIAs and modified ROMs. There is no doubt in my mind
that the design of the Dragon was copied from the CoCo, with changes
deliberately incorporated to avoid literal copying. The main differences
are:

Dragon: monitor socket for baseband composite video output in addition to RF
CoCo: RF only on CoCo 1 and CoCo 2

Dragon: parallel printer port
CoCo: bit banger serial port
(The Dragon has no bit banger)

Dragon: Extended Colour BASIC on one 16K ROM
CoCo: Colour BASIC on one 8K ROM, optionally Extended BASIC on another 8K
ROM
(In the Dragon the contents of the two ROMs are mixed up and can't be
separated into two 8K ROMs)

The wiring of the keyboard was changed from the CoCo to the Dragon.

Both keyboards have characters which exactly correspond with the internal
character set of the 6847 VDG, so in a sense the keyboard wasn't determined
by Radio Shack or Dragon Data at all but by Motorola when they designed the
VDG.

Additionally the Dragon 64 has a true RS232 ACIA with hardware support for
sending and receiving 8 bits at a time.

I think the intention when the Dragon was designed was to avoid infringing
any of Radio Shack's intellectual property rights, while still providing a
computer using the Motorola chipset and Microsoft software (where the IP
rights would be owned by Motorola and Microsoft respectively). In my view
they came pretty close, since the range of interfaces provided by the Dragon
almost matches the CoCo (analogue joysticks, 6 bit D/A converter, etc), and
not all of that was determined by the Motorola chipset or the Microsoft
software.

Possibly the success of the Dragon in the UK killed off Tandy's attempts to
market the CoCo in the UK, but evidently Radio Shack weren't bothered enough
to launch a law suit against Dragon Data. The legal uncertainty in
determining whether Radio Shack had a case against Dragon Data may also have
been a factor.

Richard


On 1/9/07, Mike Pepe <lamune at doki-doki.net> wrote:
>
> Phill Harvey-Smith wrote:
>
> >
> > If you're in the UK, and have a Dragon 32/64, then I can comfirm that
> > the 6309 works fine in that machine too, and it runs much cooler than
> > the 6809.
> >
> > Cheers.
> >
> > Phill.
> >
>
> Phill,
>
> Just out of curiosity, do you know if the Dragon 64 can be changed into
> a CoCo?
>
> I thought the keyboard was physically wired differently, but the cart
> slot is the same.
>
> -Mike
>
> --
> Coco mailing list
> Coco at maltedmedia.com
> http://five.pairlist.net/mailman/listinfo/coco
>