[jacquesm]

CoCo was an extremely nice machine with a lot of software tricks to emulate hardware that wasn't there. 6 bits a/d & d/a with a bunch of resistors and a single comparator, audio in/out and doubling as a cassette interface. Very elegant design.

Did you know that there was an English clone called the Dragon 32? And that it had 64K RAM that was never advertised but that you could use by tweaking some bits in the video chip/memory controller?

[robhawkes]

I've got my granddad's boxed and mint condition Dragon 32 sitting next to me. It looks so cool and was fun to get his hand-written code working again after over 30 years. I've been meaning to document it all!

Some fun I had with it last year: https://twitter.com/robhawkes/status/707270758393847809

[jacquesm]

Oh that's really neat!

Unfortunately I lost all my '09 stuff. Did he write in Asm or something else?

I had a rudimentary random-access storage device going on mine using a Sony TC-FX 33 cassette tape recorder. With a bit of tweaking you could control the buttons from the Dragon and it also had a nifty little optical encoder to indicate 'end of tape' that you could tie to an interrupt giving your a rough idea of where the tape was.

Even with a C120 cassette the storage capacity was terrible but it did work and it was persistent. It wore out tapes like crazy :)

That Dragon really does look mint. Beware of the big caps dying on you and taking the mb with them, it might be safer to replace them pre-emptively that power supply wasn't the best. A huge advantage the Dragon had over the original CoCo was the keyboard, it is really good quality.

[bsder]

> CoCo was an extremely nice machine with a lot of software tricks to emulate hardware that wasn't there. 6 bits a/d & d/a with a bunch of resistors and a single comparator, audio in/out and doubling as a cassette interface. Very elegant design.

It was a wonderful set of hacks. And, since almost everything was software, you had to understand what was going on rather than just magically offload it to a chip that just handles it.

The whole idea of making a dinosaur "roar" drove me down the path of sound effects, audio synthesis, ADC/DAC conversion, Fourier analysis, etc.

And the CoCo had William Barden writing books and articles that were way ahead of anything that you could have rightfully expected.

[UncleSlacky]

There was a proper 64K version (called the Dragon 64, unsurprisingly): https://en.wikipedia.org/wiki/Dragon_32/64#Dragon_32_vs._Dra...

[jacquesm]

Yes, the serial port could be added to the 32 as well, the rest was just software (some minor patches to the ROM). Not all Dragon 32's shipped with the 64K chips, and opening one up in the store wasn't an option so a little software test was useful.

We figured all this out long before the Dragon 64 was released, and a friend of mine figured out how to move the basic interpreter to RAM and relocate it. Good times.

You may want to dive in to this:

https://sourceforge.net/p/nitros9/wiki/Main_Page/