PowerPC was the processor that Apple used before they started using
Intel. Born of a joint venture between Apple, Motorola, and IBM, it
combined features of the RISC processor architecture with some of the
best features of the CISC architecture. It featured extremely low
power usage and could scale to faster performance per clock cycle
because of the way that instructions were written for it.
Most software applications are written in high level symbolic
languages. These languages have no particular allegiance to any
specific hardware architecture. If properly conceived, they are not
even aware of the existence of the hardware. However, all computer
programs have to be compiled for a specific hardware – this process
converts the symbolic language that programmer use into the machine-
specific binary instructions that computers understand. An application
that has been compiled for a particular hardware architecture will not
run on any other kind of machine. Now with many types of applications,
re-compiling for another architecture is as simple as flipping a few
switches in your development application and pressing an attractive
green button. However, this is not always possible. Some parts of the
system were only ever written and maintained for the PPC architecture,
and were deliberately removed in the massive cleanup that was Snow
Leopard. Many of the more forward-thinking developers released their
applications in what Apple called Universal versions. These had both
PPC and Intel binaries compiled separately, and placed in a particular
“bundle” format so the operating system could choose the appropriate
version at runtime. This made the software packages larger (in
megabytes) but it made it more likely that an app would survive and
upgrade from a PowerBook to a MacBook, for example.
Interesting Sidebar: So-called “scripting languages”, like PHP and
Ruby, are a special beast – they are never compiled, but instead use
what’s called a Just In Time compiler to convert the instructions from
symbolic to machine language. This makes them orders of magnitude
slower and less efficient in their use of machine resources, but the
trade-off is that the application may change while it’s running,
adding features to itself in a bit of software legerdemain called
metaprogramming, and will generally run anywhere that there is a JIT
available for the system. My Rails projects don’t care at all whether
I deploy on Solaris/SPARC or Linux/Intel, or BSD/PPC. It all Just
Works™.
When Apple switched from PPC to Intel (a CISC architecture, if you’re
keeping score) they had to do something particularly clever to allow
all the thousands of PPC-only applications to still run on the new
iron. They invented a software application called Rosetta (like the
stone) that would transparently translate application calls from PPC
dialect to Intel dialect. Rosetta was there from the earliest Intel
hardware, which I’m remembering was during Tiger. It continued through
to Leopard as a core part of the OS, and was an optional install on
Snow Leopard. But Apple had long ago signaled that the future was No
Rosetta, and in Lion, this is enforced – Rosetta will not run, and no
PPC applications will even try to launch.
If you want to use Lion, you will have to find an Intel-coded (or
Universal) application to replace any PPC application on your Mac. If
you want to show off your geek cred, you can make a neat list of all
the PPC applications on your computer by opening up /Applications/
Utilities/Terminal.app and pasting in the following one-line script
(if it got broken into multiple lines, straighten it out before use):
system_profiler SPApplicationsDataType | grep -B 4 -A 3 PowerPC > ~/
Desktop/PPCappsList.txt
After a good long while of running, you will end up with a text file
on your desktop with all the PPC-only applications. In my case, it
found tons of AppleScripts in the Adobe CS3 suite, and a few other
things I never use, like Microsoft Office from 1997.
If you’re concerned, I would definitely run that script and see if
there’s anything you can’t live without. Forewarned is fore-armed.
Walter
RISC: Reduced Instruction Set Computing. A hardware architecture
designed to support a deliberately pruned set of instructions, and to
perform many more of these per clock than a similarly-specced CISC
processor. Complex instructions are simulated by running multiple
simple instructions in parallel or serial, and because the relatively
fewer instructions are so heavily optimized, the result is that the
average program would run much more quickly and with lower power
demands that if it was run on CISC, even with the overhead of
simulating some of the instructions. Most phones and tablets and
netbooks use ARM or Atom chips, which are RISC architecture.
CISC: Complex Instruction Set Computing. A hardware architecture with
lots of specialized instructions, and a deep switching setup to send
any incoming request to precisely the right stage of the processor to
handle it. Lots of overhead, but lots of specialized hardware to
execute specific types of operations in a single clock cycle. Intel
have always primarily made CISC chips (Atom excepted), and relied on
ever-faster clock speeds and ever-tinier chip features to wring more
performance out of them.
On Sep 10, 2011, at 10:40 AM, CarolynMB wrote:
I was told to look under the Apple>More Info>Software>Applications
for the list and there’s Classic, Universal, Intel and Power PC.
What are PPC applications? I’ve aways upgraded until now when I read
that note.
I upgraded to Freeway Pro 5.5 and now the CSS Nav Menu I created in
reworking my site won’t go out of Black for the text…even though
I have colours selected for the links!
Thanks, Carolyn
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