Re: Apple IIgs Virtual Hard Disk Project - Thoughts/Different Approach?

[pitz <pitz.wong@gmail.com>]

On Apr 28, 6:28 pm, IUnknown <stevement...@gmail.com> wrote:
> The discussion regarding the 'virtual hard disk' for the IIgs had got
> me thinking a bit.
>
> I would say that the vast majority of entry-level IIgs 'hobbyists'
> have a computer with a single 3.5" and 5.25" drive. They aren't going
> to throw down $100+ dollars on a CF, SCSI or IDE adapter to get a
> decent amount of fixed storage. They likely have a PC or mac sitting
> there next to the IIgs ...
>
> What would it take to get the IIgs to boot via the serial
> connection ... as cheaply as possible?
>
> Both the IIgs and mac/pc have a serial port (one could be added VERY
> inexpensively to a mac/pc).
>
> Lets say that someone (read: me) were to develop a simple 'block
> device' host application that would run on the mac/pc that via some
> serial protocol served up a 'virtual hard disk'.
>
> After some research, it appears that while Appletalk allows the IIgs
> to 'boot', this requires special hardware on the mac/pc host (or in
> between) to properly decode the signals.... this is a total non-
> starter since we are trying to keep this thing low cost and using
> 'modern' standards..
>
> So, it would seem that without creating a 'card' with a ROM that sits
> in slot6/7 that contains the firmware necessary to operate the onboard
> UART, we are somewhat dead in the water.
>
> However, would it be possible to 'fudge' the IIgs to boot up a
> 'bootstrap' disk via the 3.5" drive, which in turn installs some
> 'firmware' at $C700, which in turn initializes the UART, and resumes
> the booting process via the serial connection?
>
> Is it possible to circumvent the IIgs firmware/boot sequence such that
> it can operate entirely from software?
> Is it possible to even write to $C700->$C7FF, or is it even necessary?
>
> I guess what I am trying to avoid is requiring NEW hardware .... if a
> user could download a disk image, which in turn would boot the IIgs
> via a 'virtual hard disk' which is really just a serial UART emulation
> of a block device it would be a panacea.
>
> I am not a hardware dude, but I am an applications programmer....
> and I know that implementing host software via a custom serial
> protocol wouldn't be too difficult. The question is whether or not is
> is possible to leverage it on the IIgs without requiring new hardware.
>
> If this is incredibly stupid or naive, please speak up and I will go
> back to my hole....

Would Antoine be the person most capable of writing this?  MountIt
mounts a PO file as a virtual disk -- it might not take a lot of work
to read/write the data through the serial port instead of a file... we
just need to write a "block transfer" protocol over the wire.  Booting
is, well, another story.