The story I heard is that Motorola went to Tandy asking them to use
their 6809 chip.
Tandy said, ok, you design a system for us with a cost of $xxx and we
will sell it.
Motorola then designed the color computer using the 6883 SAM chip which
handled almost all of the glue logic for the system. This includes
address decoding, DRAM refresh, system clock, etc.
The CoCo was made up of 3 main chips:
* 6809E CPU (The E used a 2 phase clock so they could alternate cycle
main RAM and video RAM)
* 6883 Synchronous Address Mutiplexor (took care of all of the glue logic)
* 6845 Graphics Controller Chip
Add RAM and a few Misc. chips and discretes and you have a CoCo!
Great machine but no one at Tandy realized the power of the 6809. Maybe
the CoCo III came close to exploiting all that the 6809 could do.
On 12/4/2024 10:55 AM, Tony Duell via cctalk wrote:
On Wed, Dec 4, 2024 at 4:50 PM Nigel Johnson Ham via cctalk
<[email protected]> wrote:
What is not well known is that the CoCo was actually designed by
Motorola, and appeared in their Microprocessor data book as a
double-page schematic to promote the 6809!
Wasn't it actually a suggested schematic for the 6883 synchronous
address multiplexer chip?
-tony
