[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:
> 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
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
More information about the Coco