🚀 go-pugleaf

Don Schmelling (dons@olympus.net) spake thusly:

[snip]

: I am just asking if this software has been highly optimised for the PPC.
: I do not really see much point in just recompiling software for a 680X0 Mac
: for the PPC, unless you optimise for best performance.

Most software these days are written in high level languages such as C or
C++.  There isn't much a programmer can do to optimize the code beyond 
telling the compiler that you wish to optimize for speed or for size.  The
biggest performance gains can be realized by properly aligning data, but
since the PPC and 68K alignment rules are pretty much the same, this isn't
a big issue.

Of course, if one *really* wished to squeeze every last bit of performance
out of the processor, one could hand code the critical code.  Since 
optimizing code for super-scalar RISC processors is a non-trivial task,
unless one was very familiar with the hardware, one would be more likely
to hurt performance than to enhace it.  In general, learning the 
optimization strategy used by the compliler so that structures that the
compiler handles poorly may be avoided will yield greater gains.

The point to all this is that "just recompiling" 68K code for PPC will 
increase speed tremendously over allowing the in-ROM 68K emulator to run
the original code.  Ten- to twenty-times performance gains are not unheard
of--particularly when running FPU-intesive routines.


: On the Amiga some developers write versions of their software for 68000
: computers and for 68020 or maybee 68030.

The same thing is true for Mac software as well.  There is very little 
difference between the 68020 and 68030 from a programming-model point of
view, but significant differences exist between the 68000 and the 68020.

On the PPC side, as long as one adheres strictly to the PPC family 
programming model, all PPC processors should be binary compatible.  The 
different PPC processors do require different optimization strategies to
achieve peak performance however. 


: Or is this more like Windows 95 where you use both 16 and 32 bit .dll

Not at all!  The 16/32-bit distinction is an anachronism maintained 
solely for the purposes of 80286 compatiblity.  It simply doesn't 
exist in the 68K world.

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