[Coco] How to trick Disk BASIC?, or Drivewire sans disk controller...

[Arthur Flexser]

My guess is that it's a hardware problem.  I know of no reason why any
version of Disk Basic should require the presence of a physical floppy
controller to boot up.  (I recall having once booted up a Disk Basic ROM
image from cassette before I acquired a disk controller, just to see what it
looked like.)  Have you tried putting the Disk Basic variant in the opposite
bank of the EPROM to see if it works then?

Art
On Mon, Feb 15, 2010 at 3:25 PM, Joel Ewy <jcewy at swbell.net> wrote:

> Hey everyone,
>
> I tried an experiment that hasn't yet achieved complete success.  Maybe
> somebody has some ideas about how to make it work.
>
> As a result of some discussion on the forum on coco3.com I decided to try
> modifying an Orchestra 90CC cart so that it could be used as a Drivewire
> client without a disk controller.  (
> http://www.coco3.com/community/2010/01/can-a-coco-3-sound-like-a-c64/comment-page-2/#comments)
>
> The ROM on my Orch 90 is a 28-pin ROM, which makes it easy to do this
> modification without a socket adapter.  I was successful in
> non-destructively desoldering the original ROM and installing a socket.  I
> then tested the Orch 90 with the original ROM put back in the socket.
>  William Tell Overture.
>
> Pin 26 on the Orch 90's ROM is left NC.  I wired it via a toggle switch to
> VCC and GND so I can select the upper 8K or lower 8K of a 27128 (16K) EPROM.
>  In one half of the EPROM I put a copy of the original Orchestra 90 ROM, and
> in the other half I put a copy of the Drivewire 3 HDB-DOS.
>
> When I switch it to Orch 90 it works fine.  But HDB-DOS apparently isn't
> happy that it isn't in an actual disk controller -- I don't get the Disk
> BASIC screen, but a garbled text screen.  The same thing happens if I put in
> a 2764 with the patched Disk BASIC out of a Disto Super Controller II -- the
> garbled screen looks identical.
>
> I assume that the Disk BASIC ROM is checking the floppy disk controller
> hardware and not finding what it expects.  Is there some sanity checking
> done in Disk BASIC that could be skipped if we just want to run from a
> Drivewire server and have no need of actually accessing real floppy drives?
>  One of the main objectives here is to do without real floppy drives,
> controller, or an MPI.
>
> JCE
>
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