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Re: Shit - it's all true
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Re: Shit - it's all true


  • Subject: Re: Shit - it's all true
  • From: deivy petrescu <email@hidden>
  • Date: Tue, 7 Jun 2005 10:35:29 -0400


On Jun 7, 2005, at 0:48, Allen Rongone wrote:

I am by no means an electrical engineer, but have more than 20 years experience with both CISC and RISC machines and it has been my experience that RISC processors process instructions more efficiently and faster due to their design. CISC chips use larger dies to hold all the complex instructions while RISC chips use the extra space to add more registers and buffers. By doing this they can execute more instructions per cycle than their CISC counter parts.

On RISC processors each instruction takes only one cycle, whereas a CISC processor may require multiple cycles to complete an instruction. Then take into account pipelining. On a CISC chip, if one instruction takes one cycle to complete in one pipeline and a second instruction takes 4 cycles to complete in another pipeline a misalignment could occur requiring additional resources to monitor the output and reassemble the instructions in the correct order that they were inputted. This overhead results in lower efficiency.

I understand that Intel tried to compensate for this with their MMX technology (which by the way was a big flop) and now use SSE2. However, the Intel approach to move the instruction set to hardware still remains and results in more cycles to execute a certain instruction, whereas the RISC design, eliminate the microcode from the CPU and have the compilers optimize the code, results in one instruction per cycle increases performance, not to mention the reduction of productivity costs since they use less silicon to produce a chip.

I regret that I don't have real-world numbers to prove my point but I think the philosophy behind both designs speaks for it's self. I'll agree that the CISC design is better for common integer instructions (As those used in applications that deal mainly with text and small numbers) but RISC far outperforms in areas that require complex calculations (Video, Sound, Complex imaging and scientific or engineering applications).

So I guess if you just want to write a letter or surf the web, there's no real difference, but if you really want a computer with "power" I would still take a RISC based machine over a CISC one. No offense.

Anyway, that's my $.02 worth.

Allen


well, for a "proof" take a look here: <http://www.top500.org/lists/plists.php?Y=2004&M=11>

see the damage that 2200 PowerPC chips the one people have inside their G5s, can do.
i know, this is not a "proof", certainly this is not the only reason, but it is a good indicator.
by the way, it generally blows away the 10% margin required.





deivy petrescu email@hidden


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 >Re: Shit - it's all true (From: Andrew Oliver <email@hidden>)
 >Re: Shit - it's all true (From: Allen Rongone <email@hidden>)

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