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X86 vs. RISK

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first what is X86 and RISK? i used to know but it has been a long ass time. i am sure it has something to do with the type of languages the 2 can use, but i can be wrong. well what is good about both and which is really better. i am betting X86 is better but i could be wrong

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x86 and RISC are two different things. x86 (as in 386, 486, etc.) is a processor architecture, whereas RISC (Reduced Instruction Set Computing) is a model on which some architectures are based and is opposed to CISC (Complex Instruction Set Computing).

x86 is a CISC architecture, therefore PCs, which use x86-type processors (Pentium, Athlons, whatever), are CISC computers.

Examples where RISC style architecture is used are the IBM PowerPC processor (Newer Macintoshes and Amigas), most PocketPCs (StrongARM processors) and most consoles.

Different models also imply different architectures, AFAIK.

Generally RISC is more efficient than CISC. That explains why the PlayStation 2 processor can achieve better results than say, a Pentium II at the same clock speed, or why while that console runs at 300MHz the XBox runs at 733MHz (just being pragmatic here, folks).

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Older processors are what is known as "CISC" processors: this includes the x86 architecture which is used in AMD/Intel processors. CISC processors tend to be complicated and have large numbers of different instruction types, different types of instruction etc.

RISC is a different philosophy: instead of having lots of instructions that do many different things, there is only a small number of instructions. This makes the processor a lot simpler. Because the instruction set is simpler, it is easier to add things such as pipelining, branch prediction etc. which greatly speed up the processor. Originally these things were only in RISC processors, but modern CISC processors like the Athlon and P4 use them as well (of course its a lot harder to pipeline a CISC processor than a RISC one)

Almost all modern processor architectures are RISC. This includes the PowerPC used in macs, ARM (used in GBA and various palmtops and portable stuff), MIPS (used in SGI workstations and various game consoles) and SPARC (Sun workstations and servers). This is why Macs can outperform PCs of substantially higher clock rates. Also, because they have less logic the chips run a lot cooler (the G4 cube has no fan at all)

RISC is a much MUCH better way of doing things. However, because there is so much code written for the x86 family, all processors in PCs have to be backwards-compatible so they can keep running all the old software people have been using for years. Modern PCs can still run software written for the original IBM PC.

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what fraggle said

this was true, but now it seems that risc processors and cisc have become more similar. the risc isa now has really most all of the instructions that are in a cisc chip, so they really are quite similar now.

but yeah, before there was a pretty substantial speed difference between a x mhz cisc and a x mhz cisc chip.

i found a pretty good ars technica article about it, if you'd like.


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