> The mac is going to run faster because of RISC (Reduced Instruction Set > Code). It takes less instructions at the chip level (machine code) to do > the same thing than the more "complicated" Intel x86 processors
Something is a little mixed up in that one. (And by the way, its "Reduced Instruction Set _Computer_", which is a subtile but significant change.) RISC code generally (but not always) takes _more_ instructions, precisely because they are of "reduced" capacity. In a CISC (complex instruction set computer) it takes _fewer instructions_ to do the same thing, but those instructions may be more complex and the instructions themselves might take more bytes as well since they have to specify more fields. It is true that at the "chip level" it takes less internal logic and possibly internal _microcode_ (if used) to implement a given _instruction_, but that is a different statement than "less instructions at the chip level (machine code)" because typically by "machine code" we mean the compiler's machine code output. RISC virtually always has more "instructions" by raw count than CISC, simply because RISC instructions do less and thus are more mumerous to do the same task. The reason RISC machines often outrun CISC machines is that the RISC machine instructions themselves are faster in part because the circuitry that implements them is smaller. Distance inside a chip equates to time, so more complex can slow things down. But this is not an absolute, it depends very much on the mix of steps in the particular program (as some others have mentioned). For RISC to do the _exact same task_ faster, it typically takes _more_ instruction steps, but has the potential to do even those steps faster than the CISC machine due to the overall simplicity. So understanding it takes understanding the three aspects: Instructions are "reduced" and do _less_. It takes _more_ instructions to do the same thing. But the simplicity _can_ amount to savings in OVERALL time, if the increase in speed per instruction is greater than the decrease in speed do to more instructions. Now one of the problems is that memory speed can affect the speed of the system differently in the different configurations. CISC has a sort of "data compression" effect, in that the instructions are bigger in terms of bytes, but not as much bigger as the number of bytes to do the same thing on a RISC in many circumstances. Since they do more, they tend somewhat to "compress" the code space. So if the code space memory provides the bottleneck, then the RISC machine may be slowed down. To compensate, the RISC machine is more dependent on cache memory that speeds up the access to instructions. But due to the simplifying of the remaining aspects of the processor chip, they may be able to make that "cache" memory faster by a greater degree than they can do so with the CISC. (So you see it is sort of a race, with no absolute clear winners.) The RISC machines do tend to win this competition quite well: Overall processing speed per unit of silicon area. Now does that translate to lower cost _per unit of speed_ for RISC processors? Not necessarily, once again, due to marketing considerations affecting the quantity manufactured. Higher volume can reduce the cost of the more complex and larger chip in some circumstances--and the PC does have a market share advantage. So overall, as someone else has mentioned, the differences will depend on what program is running. Interesting and trick topic. -- Gordon Elliott -- Quadlist is sponsored by <http://lowendmac.com/> and... Small Dog Electronics http://www.smalldog.com | Enter To Win A | -- Canon PowerShot Digital Cameras start at $299 | Free iBook! | Support Low End Mac <http://lowendmac.com/lists/support.html> Quadlist info: <http://lowendmac.com/lists/quadlist.shtml> --> AOL users, remove "mailto:"; Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive: <http://www.mail-archive.com/quadlist%40mail.maclaunch.com/> Using a Mac? Free email & more at Applelinks! http://www.applelinks.com
