Lots of stuff discussed in the thread here, with statements both true and false. Its all reminiscent of the old Wintel-v-PowerPC wars Mac fans waged in the 1990s. And like then, its time to cut through the statements and sort out whats accurate.
- The Wii-U's processor (Espresso) is as a whole a tri-core PowerPC G3, functionally the same as it's slower single-core predecessors Broadway and Gekko. The Xbox One and PS4's processors are AMD Jaguar APUs - chips which combine an incredibly multi-core x64 (64-bit x86) processor with a Radeon R3 graphics processor.
- The processors Intel and AMD build based on the "x86 Architecture" are substantially different from the original 8086 from the 1980s. Although word length (# bits in a single value) and address space (RAM accessible) increased, various different improvements have been made. MMX/SSE have made data structures easier to handle, integrated FPUs have made floating point calculations possible, pipelines allowed multiple instructions to run at once, and the use of L2 caches and multi-cores have speeded up multithreaded applications. Theres way more instructions as well.
- The "RISC" architecture involved several core instructions being optimised to run really quickly (1 each cycle) and all other features implemented by combining the core instructions. Innovations as Cache, high amounts of registers, Multiple cores, and Pipelining were all ideas started as RISC. Many RISC processors (PowerPC, ARM, MIPs) however used more instructions as CISC (x86, Z80) and had to execute more instructions for the same jobs.
- Its said on here that PowerPC 970 (G5) applications can run on PowerPC 750 (G3) chips just fine. The G5 uses more instructions than the 750, has a better FPU, and various other enhancements which make software incompatible with the 970 and 7400 (G4). Notably the the Altivec unit on the G4 and G5 that the G3 lacks. In the last few years of PowerPC Macs, developers had their applications run on G4 processors by default, switching to G5 mode if it detected the processor.
- PowerPC processors are infamous for heat generation and power drain as IBM and Motorola never figured out how to make them run more efficiently. The original roadmap (plan for future chip modification) at the time Apple went to Intel had a focus on making chips run even hotter for more performance. Apple went for x86 as they needed low power processors for laptops, something impossible with future PowerPC processors. Since then lower power and cooler PowerPC processors have been released with embedded systems (game systems, cellphones, tablets etc) have been released, but they can't beat the now dominant ARM.
- PowerPC is the worst processor as far as performance per watt (a term Steve Jobs used to describe the amount of raw performance against the amount of power used - the main argument he had for x86 during Apple's transitional period) is concerned. ARM have the best performance-per-watt, but currently can't match the raw power of the x64 (64-bit x86) processors. Which is why ARM is preferred for Tablets and Cellphones, while x64 is more desirable for Computers and Game Consoles.
- It would not be possible to have a G5-based Wii-U as the PowerPC 970 architecture is no longer in development, it will have compatibility issues with Wii software, and it will have to be the size of the Xbox One to hold all the cooling apparatus (the fastest G5 PowerMacs used liquid cooling). It would also have been far far more expensive to build and thus to sell.
- Although the POWER8 as a server chip is better on raw performance than any x64 part, its considerable size, heat generation, power consumption and price would make it impossible to build into a desktop system.
- A cache is used to get around slow memory access times, allowing processors to finish an instruction without waiting for the memory to respond (its saved in the cache until it can be written out). Adding more cache can make a system faster by allowing it to store more data in the cache, but is usually only really decent for batch jobs (like rendering a shape or decrypting a chunk of data), not timing-critical code (like drawing a screen or playing a sound).
- A lot of the small input/output jobs processors used to do - floating point calculations for graphics, driving serial ports etc - are now done by extra support chips in the system.
- Developing for any architecture nowadays does not require you to dabble in instruction code as theres C/C++ compilers as standard, each usually optimised to get the best performance out of a processor. However different APIs and Drivers can cause issues, as well as the quality of the compilers and other dev tools themselves (the Wii-U has being claimed to have a terribly unreliable SDK).
So considering all this, why did Nintendo go for PowerPC instead of ARM (similar performance at lower price) or x64 (to put it on level with Xbone & PS4)? Because I believe to them it was the easiest and cheapest option - they were focused on the gamepad as a whole and went for a low cost upgrade to the Wii for the supporting hardware. They didn't spend much time on the OS either - at 1GB used constantly and horrible loading times, the Wii-U is infamous for having an OS even more performance-killing than Windows Vista, with only a fraction of the functionality or desirability.
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