Re: [hatari-devel] Attaching an ACSI harddisk: 3 x Why

[Eero Tamminen <oak@xxxxxxxxxxxxxx>]

Hi,

On keskiviikko 11 maaliskuu 2015, perot@xxxxxxxxxxxxxxx wrote:
> I'm wondering why Hatari should require a reboot if a harddisk image is
> attached? It does not (of course) if a floppy image is attached. So why
> with a harddisk? With real hardware, you could have switched on your
> (for instance) Mega ST, and switch on the (for instance) SH205, since
> it's a separate unit, only after the Mega ST has come up with the
> desktop.
> 
> I have been coding software, including hardware emulators, for over 30
> years, but cannot imagine any solid reason for this restriction.

None of the Hatari developers or users has been interested enough
to add support for that.  Contributions from interested people are
are welcome.  There are some other less often used ACSI/IDE fatures
which emulation is missing.


Harddisk images are inconvenient to use and have only few use-cases:

1. Demos/programs streaming data by reading ACSI directly
   instead of going through HD driver.

-> Hatari is AFAIK already compatible with these.

2. Authors of HD driver developers testing their SW

-> HD driver authors do contribute (bugs reports, their analysis
   & sometimes fixes) to Hatari because Hatari's emulation of rest
   of Atari devices is more accurate than other emulators.

3. MiNT (as GEMDOS HD emulation doesn't work with it)

-> MiNT users use Aranym instead.  Speed is more important for MiNT users
   than emulation accuracy and Aranym has more MiNT related features
   (NatFeats MiNT VFAT driver, ethernet emulation, MMU & fast RAM support
    which will be only in next Hatari version).

4. Somebody wanting to get data out of real harddrive / its image

-> This is typically once-only use-case.


> So, I hear you ask, why should anybody want that?
> 
> I do have a problem with it right now. Those decades ago I have severely
> hardware-hacked my Ataris, to the point where they won't boot to the
> desktop if not the correct (self written) drivers are run during boot
> from the AUTO folder. I have images of the harddisks, they include those
> drivers, and using them I want to resurrect that hacked system as a
> Hatari emulation. However, if I attach the image, regardless if I check
> or uncheck the "Boot from HD" flag (why is that?)

To decide whether booting should happen from floppy or HD when both
are given.  When you give these from command line, booting happens
from whatever is given as last.


> Hatari boots from
> that image, and crashes, as those drivers do not find the corresponding
> hardware hacks. With real hardware, the solution would have been simple:
> Boot the (generic) machine without the harddisk, then switch the
> harddisk on, and run the harddisk driver from floppy. Now I could access
> the harddisk to activate and deactivate AUTO driver programs to
> eventually make the image boot. With Hatari I cannot do that, as it
> requires a reset if I attach a harddisk image.

give your HD image, but tell Hatari to boot from something else;
from floppy image, or GEMDOS HD image.  Latter is more convenient,
but how well that works depends on what your HD driver does with
already existing HD drives.


> I thought of a second way. I could have run the offending image as the
> second harddisk, as on the ACSI bus harddisk units can be daisy-chained.
> I do have an image of another harddisk that boots just fine in Hatari.
> Woefully, Hatari only supports one ACSI harddisk image. Why is that??

AFAIK nobody's needed that before.


	- Eero