2.5 GHz PowerMac G5 Dev Notes

Discussion in 'General Mac Discussion' started by Sun Baked, Jun 30, 2004.

  1. Sun Baked macrumors G5

    Sun Baked

    Joined:
    May 19, 2002
    #1
    The 1.8, 2.0, 2.5GHz PowerMac G5 Dev Notes have been posted -- and they show some interesting changes.

    Since Michiro has already found most of them, I'll not retype them.

    EDIT: Regarding the PowerTune comment -- Here is IBM's document Improvements in power management techniques in Power Architecture
     
  2. Sun Baked thread starter macrumors G5

    Sun Baked

    Joined:
    May 19, 2002
  3. 2A Batterie macrumors 6502a

    2A Batterie

    Joined:
    Jun 9, 2004
    Location:
    Out of a Suitcase, USA
    #3
    So could you dumb this down for me?

    I might have well tried to read sanscirt too. I'm a dummy, so all I want to know is if the new G5's all use the 970 or 970fx. Is there really that much difference between revA and B? Are there wider data paths?
     
  4. ddtlm macrumors 65816

    Joined:
    Aug 20, 2001
    #4
    2A Batterie:

    No there aren't, nor are wider paths needed at this time. What is needed is a lower latency memory system such as on-die memory controllers and more L2. Looking at the performance of a 2.5ghz G5 vs a 2.0ghz G5 it seems to me that scaling is always well below the 25% clock speed increase, even in Apple's posted benchmarks. That's a sure sign that the processor isn't getting the data it needs despite the impressive looking FSB.

    I think Apple's best bench (Bibble 3.1a) shows the 2.5ghz G5 at 150% faster than a P4 vs 119% for a 2.0ghz model. So relative performance is (100+150)/(100+119) = 14% boost.

    But anyway, thats off the topic. On topic, I'll also be very interested when it is definately settled what sort of 970 is in the lower-model PMacs.
     
  5. Sun Baked thread starter macrumors G5

    Sun Baked

    Joined:
    May 19, 2002
    #5
    >ddtlm

    Compare this old M. Isobe 6-19-2004 report to the Dev Note:

    New machines are the mysterious PowerMac 7,3

    The PVR of the new DP 1.8 & 2.0 was for the 970 (130nm), not the 970FX (90nm).

    The KeyLargo2 was updated in all the machines tested.

    The DP 1.8 had the original U3 System Controller (aka slower HT).

    The new DP 2.0 had the XServe U3H System Controller (aka faster HT, and ECC memory capable), but isn't using ECC memory.
     
  6. Sun Baked thread starter macrumors G5

    Sun Baked

    Joined:
    May 19, 2002
  7. Mac Maven macrumors member

    Joined:
    Jul 22, 2002
    Location:
    Los Angeles, CA
    #7
    I know this is an old thread

    I apologize for replying to this old thread, but I am wondering why Apple has always chosen not to use the various forms of error checking including, most recently, ECC. The support is built into the U3H memory controller of the (Rev B) 2.0 and 2.5 but goes unused. The Xserve uses the same memory controller requires ECC RAM. I don't think the price premium for ECC RAM is that much of an issue. If higher end PCs have used error checking for such a long period of time, why do Power Macs continue not to? It's not really a big issue, really more of a curiosity to me. I just learned today the difference between the U3 and the U3H, and that a main distinction is the significantly higher amount of heat produced by the U3H. I know that the U3H is required because of its faster rates for the DP 2.5, but I don't understand what benefit it is to my DP 2.0. Without ECC the only thing the U3H seems to do for DP 2.0 owners is register high temperature levels. Hopefully someone can give me other reasons for having the U3H. Overclocking is perhaps one possibility, but I'm asking about what extra benefit it provides to a stock machine.
     
  8. daveL macrumors 68020

    daveL

    Joined:
    Jun 18, 2003
    Location:
    Montana
    #8
    No idea on the ECC issue. It's used in the G5 servers, but the not the desktops.

    I doubt the U3H runs hotter in a 2.0 GHz G5 rev. B. The added thermal output is due to the faster (1.25 GHz vs 1.0 GHz) FSB on the 2x2.5 GHz PM. If your FSB is running at 1 GHz, there's no reason for any significant increase in heat on your machine.
     
  9. Sun Baked thread starter macrumors G5

    Sun Baked

    Joined:
    May 19, 2002
    #9
    The U3H also include a upgraded HT interace, so the bandwidth moving over the HT Bus is increased.

    A boost to 4.8 GBps on the U3H from 3.2 GBps on the U3.

    ECC and a HT change were the two major changes we saw as consumers, but Apple doesn't release information on what other changes they may have made.
     

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