[Coco] DE1 ALTERA coco3

Robert Gault robert.gault at att.net
Fri Dec 18 03:28:36 EST 2015

camillus gmail wrote:
> Thanks Dave, I look into that.
> What I want to do, is not easy to explain in e few words...LOL
> What I tried to do is, to put an existing OS9.vhd file ( sourced from some archive )
> into drive 0 in DW, and then I can do Dir on the FC ( = fpga coco ) that gives me the usual garbled of being a OS9 disk. But "dos" does give me an "ok" prompt. "bootos9" gives "sn error".
> So what is the use of vhd files and how do I use those.
> This is just playing Dave, please do not loose any sleep over it.
> I will hopefully bring my setup along at the cocofest, and then maybe some more experienced person. will set me on the right track.
> cb

The definition of a .vhd file has been around since the JVC emulator. By default 
it is a combo OS-9 plus Disk Basic hard drive. All the sectors on the drive are 
256-bytes. The first part of the drive $5A000 sectors is used for OS-9. The 
second part of the drive is the equivalent of 256 disks of 35-tracks for Disk Basic.
This type of hard drive is used with the JVC, MESS, and VCC emulators. It can 
also be used with Drivewire. With emulators, you will need the RDBDOS disk ROM 
while with real Coco hardware you will need HDBDOS.
With Emulators you will need HDBDOS to access Disk Basic images (.vhd or 
otherwise) on Drivewire. For OS-9 use, you can use RGBDOS as long as your 
OS9Boot file contains a driver descriptor set for Drivewire use.

HDBDOS is based on RGBDOS (Roger Krupski author) sold with Ken-Ton hard drive 
systems and now sold by Cloud-9; having bought the rights to the software. 
Previously I had modified the RGBDOS code to work with emulators and supplied it 
from my web site. It was incorporated into VCC with my permission.

The obvious use of .vhd drives is to store more files than most Coco hobbyists 
can use in a lifetime. If the default 8Meg drive is not large enough, it is 
possible to expand both the OS-9 and Disk Basic sections by changing three bytes 
in the RGBDOS/HDBDOS ROM. Those byte changes are also needed for switching 
between floppy images and .vhd images on Drivewire.
With Drivewire, it is possible to mount more than one .vhd image and use either 
OS-9 or Disk Basic sections of the images.

The syntax for RGBDOS/HDBDOS use is available from my web site or Cloud-9.
I have a "white paper" on the Cloud-9 site explaining how to use drives larger 
than 8Meg with Disk Basic.


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