Re: "To manually boot a disk..."

[Scott Sidley <sidleyr@jb.saic.com>]

Theusch Family wrote:

> Hiya kids.
>
> I am attempting to make a sort of "network drive" for an Apple IIe.
> It involves using a serial null-modem connection to simulate the
> actions of what the RWTS IOB does with disks, except it retrievs disk
> info from a pc running "server" software.  I was hoping to be able to
> "boot" a "file server" "disk", therefore completely eliminating the
> need for a disk drive, except for my network booter program.
>
> <snipped>
>
> What exactly would I have to read and execute from a DOS 3.3 disk
> (ProDos disk, any disk?) to start up the "Bootstrap Loader"?
> Eventually I would have to modify everything to be redirected through
> the null-modem ( !! ) but that is a different task.  If somebody could
> just explain the booting process in hazy detail, I will be satisfied
> for awhile.
>
> Would I just sorta read in Track 0, sector 0, to address $800, and JMP
> to that?
>
> Thanx.
>
> larva_jt1@yahoo.com

If you are going top emulate a DISK, all you need is the abilty to move
blocks.  A Block is
512 bytes.  You could put a small driver in the serial card rom that makes
it look like a prodos
(or pascal 1.1) block device.  The initial boot loader requests from the
server the boot block,[
the boot block on a dos 3.3 or prodos disk is track 0 sector 0 (prodos's
boot block then loads in track 0 sector 2 the second half of the prodos
boot block)] and copies it to $800 then jumps
to $801.  You can keep the boot blocks seperate on the server allowing
both dos 3.3 and prodos boots from your server.

It would not be all that fast with a 6551 ACIA, but certainly doable.

Once you work out the transfer protocol you are mostly there.