[Coco] more 1 bit madness

[Nick Marentes]

Mark McDougall <msmcdoug at ...> writes:


> > But they didn't have an 80 x 24 column screen.
> 
> Neither did the Coco.


We are talking about the CoCo3 here. 

 
> > 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.


But the interrupt handling in hardware, multiple selectable interrupt
sources and programmable timer are extremely useful. 
 

> > 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.


The CoCo3 was specifically designed to run OS-9 Level 2. That's why the
interrupt system was designed as it was. The CoCo3 also came with 128K
expandable to 512K as well. The standard C64 was 64K throughout it's life
unless one moved to the less popular C128 (and then used it like a C64 for
99% of the time).

 
> > 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.


What about Disk Basic in ROM? I'd much rather program disk I/O on a CoCo
than a C64! Also used industry standard drives. With OS-9 (or modded Disk
Basic) one could also used 80 track and double sided.

LOAD"*",8,1  to get a disk directory sux in comparison to DIR.

 
> 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!

The flashing bands of out-of-video-sync color were entertaining to watch
during a disk load once you understood it wasn't your computer crashing.   :)


Nick