I have a few points I wanted to make here and there while reading :
1- One person said that moving to a x86 architecture would require the major application makers like adobe, microsoft, macromedia... to commit to port their application. This is true and it's the problem here. Microsoft already said it wasn't sure it would make future version of office for mac due ( allegedly ) to poor sales. If apple move to x86, they definitely won't make it. The hacker community is strong and whatever protection apple put in their computer to prevent XP from being installed in mac or more importantly, OSX from being installed in pc WILL be overcome. Apple will be a competitor to microsoft and in this scenario, microsoft will certainly not help apple by porting office.
2- A few post talked about the advantage of G4 being altivec. Altivec is a pretty good SIMD ( single instruction multiple data ) processing unit but every processor has one. Apple just marketed theirs better. MMX, 3Dnow, SSE, SSE2 in pentium and athlon are "equivalents". MMX for one, I can say it's inferior. It's a poor 64bit vector unit extremely limited in it's usage. Each instructions has been designed to do one task and it's so specialized that it's pretty hard to use in for anything else. But the others appeared after MMX and while I don't know them enough to say how they compare to altivec, they are definitely improvement over the MMX.
3- OSX is way more overhead than XP. It offers more possibilities, features, processor intensive eye-candy which makes it slower. It's a design choice. A car that would run without radio, AC, heater, headlights,... just the bare minimum ( like a race car ) would be faster and more efficient but the goal of a car is not only speed, it has to be usable. Heater is necessary in winter and headlights are necessary during night. For computers, it's the same thing. If you want real raw power ( like supercomputers ), get rid of the gui, get rid of the fancy video card and run deamons ( faceless applications, no interface ) or maybe text based interface. No need for a dictionary, text to speech, services, multiple fonts. Everything is about trade-offs and apple decided to go more for "confort and features" and less for "raw power" than microsoft.
4- A few post talked about power consumption and I think missed the real point. The thing is not about electricity price. Do you hesitate to change the 60W bulb for a 100W one when you don't see well enough in a room ? The point is about noise ( +power = + fans ) and more importantly : laptops. iBook claim to have 6 hours of battery life. Someone who has one tell me the real battery life they have. On PC, they don't claim more than 2hrs battery life and I don't know what they do during those 2 hours ( reading web pages ? ) but my programmer friend never got more than 1h30 on it ThinkPad and it's usually less than that.
5- If going to x86, why go AMD ( marketing ? ) because right now, Intel definetly has the advantage.
http://www.tomshardware.com/cpu/02q4/021114/p4_306ht-10.html
6- And last but not least, discussion came to 64bit over 32bit processor. One thing I want to make clear is that 64bit IS A DISADVANTAVE. It will be necessary one day to overcome the 4gig addressing space limit but it WILL BE A SLOWDOWN. 64bit means bigger memory requirement ( memory is cheap but also think that it also occupies more space in caches ie less element in cache so more cache miss ) slower throughput ( a 128bit bus can move 4 32bit chunks or 2 64bit chunks ) and 64bit integer treatment is mostly useless on consumer machines. Is there a programmer here that can tell me he uses 64bit integer intensively in a consumer application ? The today 32bit G4 uses 32bit address, 32bit instruction and 32bit integer registers and ALU ( arithmetic and logic unit ) but has 64bit floating-point unit and register and 128bit vector ( altivec ) unit and register.
Perhaps we should go back to 16-bit because 32-bit is a disadvantage? A processor in itself doesn't have memory requirements, so I have no idea how you are saying there is a bigger memory requirement. Next, how can you say that a 64-bit chip has slower throughput? Yes, a 128-bit bus can move 4 32-bit chunks or 2 64-bit chunks. I don't think they're going to leave the bus width the same while increasing that of the processor, it would be self-defeating...it wouldn't be any slower though, it would still be the same speed should bus width stay constant.
