[Coco] Re: atari USB device

John R. Hogerhuis jhoger at pobox.com
Fri Nov 26 15:05:34 EST 2004

On Fri, 2004-11-26 at 11:38, jdaggett at gate.net wrote:
> Mark
> The main problem in making any USB cartridge backward compatible with the Coco 
> 1 and  Coco 2 is that Color Basic and Extended Color Basic set in ROM and that 
> precludes any simple ram patch of the ROM code impossible. The Coco 3 copies all 
> those ROMS into ram and can be patched rather easy. 
> What has to be done is the cartridge would have to have the Color Basic and/or 
> Extended Color Basic ROM modified and stored and decoded at address $A000 to 
> $BFFF and/or $8000 to $9FFF along with the USB software at $C000. First 
> estimates is that the KEYIN subroutine is all that is needed to be patched. In fact 
> Color Basic 1.2 is easier to patch than Color Basic 1.0.  The KEYIN subroutine is 
> where the computer looks at the PIA port and gets the value from it. 
> It is not impossible but by far can be a bit more complex than that  of the Atari 
> versin and more hardware. Definitely more cost.

Yep, more cost. No reason to complicate this simple hardware device by
adding built-in storage, at least on the first iteration. It's just a

OS-9 will work fine if we simply write appropriate drivers, loaded at

The Coco 3 under BASIC or DOS can be patched at runtime.

Those that take 0-time-to-boot seriously will come up with something
completely in ROM as an internal upgrade, or something on another
multi-pak slot.

The simplest ROM improvement for use with this USB controller would just
go look for an attached USB storage device with a special file on it and
use as a patch or ROM image to boot the machine. Assuming USB Storage
will work with it, which I don't have any hard reason to believe that it

-- John.

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