Question

How do other processor architectures (m68k, PowerPC, SPARC, ARM, Z80, MIPS, Itanium) compare to the x86 and x86-64 architectures?

What does it mean when a processor is a CISC or a RISC machine?

Also, how do you decide which one is best?

Answer 1

I'm not sure about a lot of the architectures you listed but MIPS and ARM are RISC architectures. x86_32 and x86_64 are CISC architectures.

ARM CPUs are much more energy efficient than x86 CPUs. They're a very serious threat to the Intel Atom x86 architecture.

"Reduced instruction set computing, or RISC ( /ˈrɪsk/), is a CPU design strategy based on the insight that simplified (as opposed to complex) instructions can provide higher performance if this simplicity enables much faster execution of each instruction. A computer based on this strategy is a reduced instruction set computer also called RISC."

"A complex instruction set computer (CISC, /ˈsɪsk/) is a computer where single instructions can execute several low-level operations (such as a load from memory, an arithmetic operation, and a memory store) and/or are capable of multi-step operations or addressing modes within single instructions. The term was retroactively coined in contrast to reduced instruction set computer (RISC).[1]"

both from Wikipedia.

To decide which one is best, you have to think about your needs. Proprietary programs will typically work only in x86 and, in the near future, also on ARM (for example, Windows 8 for ARM). Also, companies will likely charge you twice for the same program for a different architecture. If you're entirely dependent on free and open source software, then this is a non-issue (look at Debian with all the same programs compiled for each architecture it supports).

Another issue to consider is battery life/energy efficiency/cost of electricity. In this sense, I think RISC architectures like ARM will excel and, I wouldn't be surprised if ARM starts "taking over the world." I also read that AMD was working on an ARM processor but I'm not 100% sure.

Sorry, for not answering your question 100% and also sorry if anything I said is not accurate. I have yet to take a computer architecture course but I am nonetheless interested in this kind of stuff.