Re: Booting problem (Prodos)

[dempson@actrix.gen.nz (David Empson)]

In article <37bgsa$qkh@er5.rutgers.edu>, Kid <neiderma@er5.rutgers.edu> wrote:
> 
> >The boot block looks for and runs a file called "PRODOS" in the root
> >directory of the disk. It must be a sapling file (>512 bytes) and be a
> >SYS
> >(type $FF) file.
> 
> What could be stripped out of ProDOS-8 (the SYStem file) if I wanted
> to save disk space on a 5.25" disk?  Say keeping most of the disk
> IO routines (chucking LOCK and UNLOCK and VERIFY and whatnot)

LOCK, UNLOCK and VERIFY are BASIC.SYSTEM commands, not part of
ProDOS-8.  LOCK and UNLOCK use the ProDOS SET_FILE_INFO call, which is
required by other programs anyway.  VERIFY uses the standard ProDOS
READ call.

You don't need BASIC.SYSTEM if you are only launching other SYS files.
If you have an 80-column IIe or a IIc or IIgs, ProDOS-8 1.9 and later
have a decent program selector built in.  You need a SYS file on the
disk with a name ending in ".SYSTEM", which will be launched when you
boot the disk.  Alternatively, use ProDOS-8 2.0.3 (requires a 65C02
microprocessor), which will go to the program selector if there are no
".SYSTEM" files.

Plug time: my QUITTER program (renamed to QUITTER.SYSTEM) is much
smaller than BASIC.SYSTEM, and could be used as a program launcher
with any version of ProDOS and any Apple ][.  I use PRODOS +
QUITTER.SYSTEM as my main launch platform on my second IIgs, which is
floppy-based.  I am using 3.5" disks, of course, so I don't have to
worry about disk space as much as you would on a 5.25" disk.


There really isn't anything significant you could remove from PRODOS
without crippling the operating system.  With a lot of hard work, you
could probably remove the IIgs-specific stuff in ProDOS-8 1.2 or
later, but it would require disassembling a large portion of the
operating system loader and relocater.  You might be able to get rid
of several little pieces, such as the clock driver, but they would be
pretty widely scattered.

A possible solution would be to use an older version, e.g. ProDOS
1.1.1, which has no IIgs-specific code and is somewhat smaller than
current versions.  You lose some features, e.g. the 80-column program
selector, SmartPort drive remapping, and the potential to undelete
files, plus you'd get some old bugs in the operating system back again.

> and most of the slot stuff and all the video stuff.

What slot stuff and video stuff?  ProDOS's video support probably
consists of identifying the 80-column card (needed for other
applications anyway), displaying the boot-time "splash" screen, the
program selector, and a few "crash" error messages.

Slot support consists of locating disk controller cards (you hardly
want to lose that!), setting up the device driver table, setting up
the /RAM disk (including the driver for it), and in recent versions,
handling SmartPort device remapping.

Come to think of it, you probably can't get rid of /RAM without
causing problems with some programs that expect it to be there so they
can disconnect and reconnect it.

> I was thinking that it would be nice if I could make the ProDOS file
> maybe 2/3 or 1/2 of what it is now, but be able to boot it and run
> ShrinkIt and ZLink.  

Maybe if you spent a couple of months doing a reasonable disassembly
and rewriting parts of it, you might be able to save about 8 blocks
(no clock driver, no RAM driver, no program selectors, no SmartPort
support, no IIgs support, no title screen).  Why bother?

> This would be for my own use.  Just to try out.  Thanks for not
> saying it's a silly idea. :)

Not in so few words, anyway.  :-)
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand