[Coco] more 1 bit madness

[Mark McDougall]

On 22/01/2014 3:17 PM, Nick Marentes wrote:

> But they didn't have an 80 x 24 column screen.

Neither did the Coco.

> Lower resolution graphics (No 640 x 200)
> No advanced interrupt handling.

Don't see how this automatically translates to lower cost. In fact, the
custom graphics chips would've been no cheaper to produce than the GIME.
And interrupt capability is nothing more than routing pins to the CPU
interrupt line(s); not a great cost to develop. Yes the GIME has IRQ/FIRQ
but a basic 'interrupt controller' is trivial even back in those days.

> The ability to run a multi-tasking multi-user industry standard OS (Os-9).

This was more a by-product of the fact that OS9 happened to be available
for the 6809, and nothing similar for the 6502. It doesn't directly affect
the cost of the design in any way.

> Slower floppy drive access.

There was nothing inherent in the Coco designs that increased the cost to
support 'faster' floppy drives. Both C64 and Coco had cartridge ports; not
much else is required to add floppy drive capability. The Coco had some
in-built select logic for disk I/O access, but that's also trivial.

The C64 floppies are only slow due to the crappy serial (IEC) bus they
decided to use. They also spent money developing their own controller
(which was another 6502) rather than plonk a COTS controller chip on
there. An expensive dog's breakfast IMHO!

Regards,

-- 
|              Mark McDougall                | "Electrical Engineers do it
|  <http://members.iinet.net.au/~msmcdoug>   |   with less resistance!"