Core Duo vs. AltiVec for apps like iMovie

Discussion in 'Mac Pro' started by sigamy, Jan 11, 2006.

  1. sigamy macrumors 65816

    Mar 7, 2003
    NJ USA
    I currently own a 1Ghz FP iMac G4. Thinking about getting one of the new Intel iMacs. I know that iLife will run native. I'm just wondering how is Apple getting the performance when these chips don't have Altivec? Is it just due to the fact that there are two cores doing the work?

    And a follow-up question...should I expect to see 4x the performance (on some tasks) when comparing my 1Ghz G4 to the 2.0 Ghz Core Duo?

  2. mrgreen4242 macrumors 601


    Feb 10, 2004
    I am nto going to try and answer these questions definitively, but from what I know Altivec is a floating point and SIMD instruction set (that means it's doing the same thing to multiple pieces of data at once; which is good for multimedia stuff like encoding/decoding) that is good, but not THAT much better than SSE3, which is the set of functions that are comparible on the Pentium 4 and M series chips (Yonah is a version of the Pentium M, and is I think the first to have SSE3).

    So, an application that is compiled and optimized for the Mac Intel architechture will presumably take advantage of SSE3 and you shouldn't see a ton of power loss. Especially if you are comparing a single CPU to dual core, and also an overall slower chip (1ghz G4) to a significantly fast one (1.6-2ghz Pentium M).

    I would guess that you will see a 4x improvement on almost everything going from a 1ghz G4 to a 2x2ghz P-M, so long as you are using Universal Binary software that has been optimized for SSE3. Running Altivec code through Rosetta, I am just speculting, you will be doing good to get the same or just slightly better level of performance you have on a 1ghz G4.

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