[Coco] more 1 bit madness

[Simon Jonassen]

Hmmm....

6502 as a controller and 2K onboard ram in the drive itself is VERY
USEFUL......

Yes it uses serial (normally 1 bit), but you can actually "steal" the ACK
line to provide 2 bit transfer...

If you have ever seen any recent c64 demos, you would think again about
calling the drive slow...

Most demos use irq driven "on the fly" loading..... 

/Simon :-)
 

-----Oprindelig meddelelse-----
Fra: coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com] På
vegne af Nick Marentes
Sendt: 22. januar 2014 19:49
Til: coco at maltedmedia.com
Emne: Re: [Coco] more 1 bit madness

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




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