[Coco] HDB-DOS Question

Robert Gault robert.gault at att.net
Thu May 14 08:55:56 EDT 2020

Just as a reminder :) for RGBDOS and HDBDOS the ROM offset for the Basic disks should be $5A000 and 
found at $D938=$5 $D939=$A0 $D93A=$00.
Of course the values can be different depending on the actual hardware and desired sizes. The above 
is used for MAME and VCC but was much smaller in the original hardware that came with RGBDOS systems 
before the software was bought by Cloud-9.


Gene Heskett wrote:
> On Thursday 14 May 2020 05:27:54 Jeff Teunissen wrote:
>> On Thu, May 14, 2020 at 3:42 AM Gene Heskett <gheskett at shentel.net>
> wrote:
>>> On Thursday 14 May 2020 00:22:30 tonym wrote:
>>>> Anyone know how to pull the "offset" you entered when creating a
>>>> drive?
>>>> Years ago, I setup a Glenside IDE with a 512MB CF card, and
>>>> generated the HDBDOS ROM file, which I flashed to my SDC. Can't
>>>> find the paperwork where I wrote the information down, but I think
>>>> I still have the .DSK image I used when generating.
>>>> Is there a peek() I can do while under the HDB ROM that will give
>>>> me the offset I used?
>>> That offset, generally, is the first 3 bytes of the drive, (DD.SIZ
>>> in the defs) plus 1. Everything beyond that point that is still
>>> reachable with that 24 bit address limit, is free for rsdos vdisk
>>> use.
>> He wasn't trying to find out the size of the disk, he was trying to
>> find how big a disk to make to match the offset burned into his
>> HDB-DOS ROM. That information can only be gotten by reading the ROM
>> itself.
> Ahh, generally the disk and the rom match. if they were configured at the
> same time.  But I haven't done the peeks in 25 years, so I picked the
> way I am familiar with.
> Cheers, Gene Heskett

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