Re: ProDOS...

["Charles Stephens" <charles_stephens@hotmail.com>]

"Louis Schulman" <louiss@gate.net> wrote in message
news:8r8l15$1h0e$1@news.gate.net...
> In <1ehssze.jy4jskefvttoN%dempson@actrix.gen.nz>, dempson@actrix.gen.nz
(David Empson) writes:
> >Roy and/or Janet Miller <millers@inetnebr.com> wrote:
> >
> >> Phoenyx wrote:
> >> >
> >> > My comment about the P8 compatibility is still valid, just as David's
is.
> >> > Any new or upgraded OS would loose 80 to 90 percent compatibility
with
> >> > system applications due to the way the ProDos/Apple II system is
designed.
> >>
> >> But would a full implementation of SOS do that?
> >
> >SOS would be no better than any other non-ProDOS operating system.
> >
> In fact, while SOS and the Apple /// may theoretically be more capable
than
> an Apple //e and ProDos, in practice the opposite is true.
>
> This is primarily because the genius of the Apple II design was not
> implemented in the Apple ///.  In the II, each slot card typically carries
> its own driver in ROM, which automatically attaches to ProDOS.  Thus, you
> have true plug and play, no configuration problems, and any hardware you
can
> think of can be added without problem.

Well, yes and no.  Most II series cards have known read and write vectors
and if they were nice Pascal style ID bytes.  However these were only good
for serial and parallel cards.  You still needed a driver of somesort.  Most
exotic cards usually were bundled with applications that used them directly.

> The opposite is true in the ///.  All hardware works through drivers that
> have to be configured and loaded into RAM at boot time.  Even though an
> Apple /// may have more base memory than a II, it is quite common to run
out
> of memory to load drivers.  Also, the drivers take up a lot of space on
the
> boot disk, and it is common to run out of room there as well.

This in the long run is probably a smarter way to go.  ROM is ROM, at least
with software you can easily update the code and distribute it to customers
than swapping out IC's.  However, RAM is precious.

> ProDOS is superior to SOS, because it uses Woz's original ingenious
> design for the II.  This design is still better than anything before or
since,
> imho.

SOS was probably a better OS only because it had better hardware to run on.
The II's memory space was haphazardly laid out. Remember, the original II's
shipped in both 4K and a whopping 16K configurations.  No body even thought
about going beyond 64K (or even 48K).  Ahh, how times have changed.

What should have happened was to have ProDOS dictate explicit memory
management.  If you wanted X amount of pages, you got them and then if you
wanted to use them you asked the MM system to copy in the memory to location
you specify.

I presume the III could do this in hardware rather than copying the data
back and forth.  This is easy because the memory in the III was contiguous
in harware and the ASIC could have 256 pointers to anywhere in the physical
memory space.  This is how it is done in most modern MMU systems.

The II series has no such MMU and can only bank switch clumsily.  It is easy
to get confused with which bank is in for the 48K main memory and which 12K
bank is in for the upper memory (plus the 4K in the lower 12K).  Uuugh, no
wonder it was easier to use a RAM card!

cfs