What is it about the Intel Macs that....

[FunkFaker]

....that makes it necessary for most software developers to rearrange their programs to suit?

I'm just trying to understand a bit about what the differences are between powerPC and Intel macs that makes this crucial.

Thanks in advance for the info!

Tommy

[theblue1]

A silly analogy might be helpful.

Imagine, for purposes of analogy, the CPU as a handheld calculator.

Early calculators were very similar because they just had basic functions, add, subtract, multiply, divide, maybe a square root function, etc.

But as calculators got more complicated, their keyboard layout changed -- and the way that the calculators expected YOU to enter complex equations became variegated as one calculator manufacturer or another thought he had a 'better way' to interact with the user.

In the analogy above, you, the user are like the OS. You know what you want to do -- but you need to be able to break that down into the simple -- and the not so simple, complex instruction sets that the chip makers tend to build into their chips.

We've seen a move to change the way we approach those instruction sets, with newer generations tending toward smaller instruction sets -- but with other interior architectural changes that balance this apparent reduction in complexity.

A site like www.Anandtech.com will provide you more information on chip design and comparisons between the main families of chips from the major manufacturers than you'll probably ever want to know.

[T_R_S]

This is the simple explination.
A Power PC is a RISC microprocessor, an Intel chip is a CISC micropro.
A RISC chip rquires fewer lines on code to execute the same calculation as a CISC chip.

[Tonal-Retentive]

Originally Posted by T_R_S

This is the simple explination.
A Power PC is a RISC microprocessor, an Intel chip is a CISC micropro.
A RISC chip rquires fewer lines on code to execute the same calculation as a CISC chip.

Though as RISC processors have developed the lines have blurred b/t the "Reduced" instruction chips vs. your standard CISC (Intel).


FunkFaker, one major difference is the way bytes are stored in memory, with the PPC chips storing high-order bytes in memory first, and Intel (CISC) storing them opposite.

A compiler can solve problems like this (Xcode for example) but a lot of people use CodeWarrior, so they have to move their code into Xcode, and then any optimizations written for the PPC (like Altivec) have to be translated into SSE optimizations. So you have a head start if you wrote your code in Xcode, but any "tricks" used will probably need hand-written adaptations.

[dkatz42]

Originally Posted by FunkFaker

....that makes it necessary for most software developers to rearrange their programs to suit?

The heart of the matter is that the two processors speak a different "language" (the patterns of bits that tell the processors what to do.)

In the best of all possible worlds, software written by the programmer ("source code") is done in a language that is not specific to any processor ("platform-independent"), and one that is at least somewhat human-friendly (with words like "if" and symbols like "+".)

The software is than translated into processor language ("object code") by another program (a "compiler.") If the source code is truly platform-independent, all that should be necessary is to recompile the source code with a compiler that generates object code for the new processor. The Mac development environment ("XCode")generates object code for both PPC and Intel and wraps them both up in a single package ("Universal Binary.")

Usually it's not as easy as this. There are a number of impediments, some blatant and some more subtle:

1) The software was developed in an older development environment (not XCode) and first has to be made to compile under XCode.

2) The software contains code written to take advantage of very specific features/instructions of the processor. This code needs to be rewritten for the new processor (or in a more abstract, processor-independent way.) This is often the case in DSP software (plugins and the like) as performance improvements are possible.

3) The software contains code that accidentally only works on the old processor (usually due to things like the order that individual bytes are stored in memory.) These can be hard to find, and necessitate going through the code carefully.

This process can take anywhere from minutes to months, depending on how careful the software engineers were when they originally wrote the code.


There is an additional dimension to this, which is the O/S. Most applications have software that implicitly "knows" what o/s they're running under, and getting something to run under multiple o/s's can be quite an undertaking unless careful design was done up front. This is one reason why you're not going to be seeing Windows .exe apps running under MacOS, even though both are Intel object code.

[octatonic]

Originally Posted by FunkFaker

....that makes it necessary for most software developers to rearrange their programs to suit?

I'm just trying to understand a bit about what the differences are between powerPC and Intel macs that makes this crucial.

Thanks in advance for the info!

Tommy

To grossly oversimplify.
To a french person you speak french.
To a german person you speak german.
Same with computers but they cannot learn each others languages.

[dkatz42]

Originally Posted by richmondjames

To grossly oversimplify.
To a french person you speak french.
To a german person you speak german.
Same with computers but they cannot learn each others languages.

More like you speak Esperanto and bring your handy Esperanto/French translation box with you when you go to Paris. But when your company transfers you to Hungary, you need to get a new translation box (and not everything you say translates precisely to Hungarian, so you need to speak a bit more simply.)

[octatonic]

Originally Posted by dkatz42

More like you speak Esperanto and bring your handy Esperanto/French translation box with you when you go to Paris. But when your company transfers you to Hungary, you need to get a new translation box (and not everything you say translates precisely to Hungarian, so you need to speak a bit more simply.)

Sigh... there is always one, isnt there?

[FunkFaker]

Thank you all for your info!

The concept is a bit clearer, but I'm still trying to understand what is entailed in the actual translations. However, I think I have enough to get me started.

Thanks again for the support!

Tommy

[manning1]

faker....
there are many complex issues going to any new platform or computer architecture. one main one would be that the developers used a set of programmers tools to code on G5 macs. eg....plug ins for example.
now...if those programmers tools are not yet developed for intel macs this poses a problem for the deveoper porting over from one processor architecture to another. so things have to happen in a sequence. firstly programmers tools have to be available on intel mac then the programmers can recompile their applications on intel macs. unless apple provides a seamless translation whereby a G5 mac program can run on a intel processor. think of it simplistically that its not an easy task to install a chevy engine in a ford for example or vice versa. it CAN be done with some engineering prolly. but prolly some re-engineering has to occur. just a simple example.