[Coco] mess HD problem
Robert Gault
robert.gault at att.net
Wed Aug 6 22:46:12 EDT 2014
Bill Nobel wrote:
> Hmm, Robert your post pointed out something I have wrong in my /DD descriptor.
> Mine is currently set to $FFE0 and I’m using EmuDsk. I do only use one vhd and
> everything works good. I now need to look at the source now to see if hpa is
> even used.
>
> Bill Nobel
>
It is not used. :(
When Alan wrote emudsk, there wasn't a need to check the descriptor for
anything. The size of the OS-9 .vhd section was hard coded to $5A000 and only
one .vhd image was used. That meant the I/O port could also be hard coded.
With the advent of a second .vhd drive, I had the code check the descriptor for
the drive number 0 or 1.
The version of emudsk on Sourceforge will not work with the second .vhd drive in
the JVC emulator because there is no code for the $FF80 set of I/O ports.
That would not be difficult as you could use a register to point to the port
base instead of using extended addressing. When switching drives, you would
alter the register by $60; $FF80+$60=$FFE0.
Robert
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