Re: Is this true?

[et472@FreeNet.Carleton.CA (Michael Black)]

JWolf6589 (jwolf6589@aol.comnospam) writes:
> I read this quote: "All PC-compatible computers (even a 1Ghz PIII) are equipped
> with hardware to provide this backward compatibility and are therefore able to
> execute the large no. of applications which have been developed for
> PC-compatible computers in the last 20 years."
> 
> If PC's are designed so smart, howcome the MacOS or should I say OSX is not
> designed to be 100% backward compatible with all software developed for any
> Apple computer ?  I mean all my Apple II software will not work on a OSX OS
> without a emulator, and some of my MacOS classic software will not run under
> OSX.  It is true OSX does offer a classic compatibility mode, but using this is
> KINDA like using a emulator.  
> 	Maybe I am blind, but I know that when I use Windows XP I seem to have an
> easier time using older Windows 98/95 software or even DOS software, than if I
> were using Mac OSX and using ProDOS (Apple II software) or Mac OS classic
> software.  
> 
>[stuff deleted] 
> 
> John
> 
> 
> 
"IBM compatibles" aren't smart, it's just that as improvements have
come it has been in the form of additions to the basic form, rather
than radical change.

There is nothing in common between an Apple II (a 6502 CPU) and a MAC, and
there is a fair difference between a 680X0 MAC, and a PowerMac.  Each time
the CPU has changed, it's been a radical change, and the rest of the
computer has changed too.  

The original "IBM PC" used an 8088.  Everyone in the line since then
has been the same basic CPU, but with added instructions and sometimes
more hardware.  After a certain point, the real change is speed; an
80486 is pretty much an 80386 with a built in math coprocessor.  Some
of the peripheral hardware has changed; if you want to run a program
from about twenty years ago that used a Hercules monochrome display,
there might be problems running that software on a present day computer's
video system, but the CPU from today could still run the instructions
in the software, as if the CPU was still that original 8088.

Apple has changed hardware dramatically from time to time over 25
years, which makes the software incompatible.  The further the Mac
gets away from the original MAC, the less reason to stay compatible,
so the harder it will be to run older softare.  One can argue over
which choice is the best, but they are basically philosophical decisions
over CPU and computer architecture.

When the PowerMac came along, the early versions of the system software
for it did include some level of compatibility, I gather in the form
of an emulator for running 680X0 programs.  But that was about a decade
ago.  The emulator slows things down, there is plenty of newer software
that runs directly on the PowerMac, so why bother keeping the compatibility?

   Michael