Re: Apple II IDE interface

[pausch@saaf.se (Paul Schlyter)]

In article <1erf6ev.hpye5pd9idbmN%dempson@actrix.gen.nz>,
David Empson <dempson@actrix.gen.nz> wrote:
 
> I don't know how CP/M might work, but Pascal does support drivers loaded
> from a boot floppy.  You would need a ProDOS driver in firmware to
> support booting Pascal from the IDE card.
 
CP/M has no inherent support for loading device drivers.  All
device-specific stuff is supposed to be implemented in the BIOS by
the vendor of that hardware.  However, nothing prevents a vendor from
implementing loadable device drivers in their particular BIOS.  The
Appli-Card implemented a method to load such drivers for instance,
however you had to be an OEM to get access to info about how to write
such drivers.  The Appli-Card device drivers were supposed to be
implemented as 6502 code and be stored in some free area in the 6502
RAM (the Appli-Card's Z80 had 64K RAM of its own, leaving all the
Apple RAM to the 6502; part of that RAM was used for I/O through
the 6502 though, and the Z80 had to pass *all* I/O via the 6502).
 
Also: nothing would prevent you from writing a CP/M program which
patched the BIOS and then reserved some resident area (probably some
reserved area outside the TPA and BDOS), storing the driver there.
 
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