[Coco] Why do a next Gen CoCo?

Aaron Wolfe aawolfe at gmail.com
Fri Nov 19 01:34:06 EST 2010

On Fri, Nov 19, 2010 at 1:15 AM, Mark McDougall <msmcdoug at iinet.net.au> wrote:
> On 19/11/2010 1:06 PM, Steve Bjork wrote:
>> Remember, the CoCo4 Project did include an CoCo1/2/3 emulator that would
>> work most Color Computer without any mods.
>> But the emulator did not stop there. You could also could also use the
>> optional I/O card to hookup CoCo Joysticks, Floppy Disk controller card
>> and
>> other devices to the CoCo 4 system. The I/O card would have its own
>> Micro-CPU chip to talk to the CoCo hardware and USB interface to the PC.
>> Best of all, it was deign to fit inside a CoCo case and use the CoCo
>> keyboard. It would look and work just like a CoCo 3.
> I am guilty of not taking the time to go back and re-familiarise myself with
> your project - sorry! :(
> What I'd be interested to know is whether or not your 'specification' is
> something that could feasibly be implemented in an FPGA. It'd be great to
> have that option as I discussed in another post (rhetorical question, I
> don't expect you to answer that here!)
>> For the CoCo, the device would be about the size of a rom pak and
>> interface
>> into a PC as a USB device. Its operation would be like DriveWire without
>> the
>> need to mod DECB or OS-9. An OS-9 driver could be written to talk to the
>> device in a "native" mode for faster byte transfers. (And be upto 8 times
>> faster than drive wire too.)
>> The plan is to create a working device to the CoCo first and then release
>> the design to public domain for others to use with their non-coco systems.
> I can understand the utility of emulating the WD controller for connecting
> to the Coco. Whilst I applaud the efforts of Drivewire (and I don't mean to
> detract from it at all) it has always bugged me that you need to patch DECB,
> which means it isn't 100% compatible with all software. And the tight code
> loops also mean you're restricted to what CPU speeds you can run it on.

FWIW, when using DriveWire with Coco3FPGA, you do not have to patch
DECB or use special drivers in OS9.  Gary has implemented a FD
controller that does almost exactly what it sounds like Steve's
project does.  It presents a "real" floppy controller to the CoCo and
speaks DriveWire behind the scenes.  There is even a special
passthrough mode in OS9 that gives high performance and allows the
extended functionality of DW version 4.  In all modes the speed is
better than 'regular' drivewire, although we have only got it working
up to 460800bps (4x normal DW) due to limitations on the DE1 board.
On other boards perhaps it could go even faster.  This is all stuff
that is tested and working right now.

> I'm also assuming you have some type of modern, high-capacity storage device
> connected to the other side that stores many floppy disk images?!?
> Where you lose me is connecting this to a PC via USB. I don't see the need
> for it in this case, as the WD controller can be emulated within the PC more
> efficiently. You also have the option then of accessing floppy images on the
> host file system, as well as external media such as SD, USB.
> Have I missed something in your explanation?
> Regards,
> --
> |              Mark McDougall                | "Electrical Engineers do it
> |  <http://members.iinet.net.au/~msmcdoug>   |   with less resistance!"
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