64 bit PPC 970...ehh?

Discussion in 'Macintosh Computers' started by zuggerat, Jun 9, 2003.

  1. zuggerat macrumors regular

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    NY
    #1
    when the ppc 970 enters the powerbook line (or any line for that matter) what exactly will that 64-bit processing power do for the computer?
     
  2. job macrumors 68040

    job

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    #2
    Six words

    Bus speed.

    Bus speed.

    Bus speed.


    :D

    Seriously though, the FSB and the increased memory capacity will inherently speed up processes.
     
  3. Gymnut macrumors 68000

    Gymnut

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    Apr 18, 2003
    #3
    800mhz FSB and 167mhz does not an equal make. Go figure.
     
  4. cb911 macrumors 601

    cb911

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    BrisVegas, Australia
    #4
    i don't quite understand what you're trying to say... that 800MHz is nowhere near 167MHz? yep, that's right one of the big reasons the 970 will haul ass.

    if you want to find out more about 64-bit computing you should check out arstechnica.com .
    they have a really good article about 64 bit and they compare it to 32 bit. it explains it very well, definitely worth taking the time to have a look.
     
  5. WannabeSQ macrumors 6502

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    Oct 24, 2002
    #5
    if you are just asking about 64 bit, and not the 970 specifically, the main boost is the amount of RAM you can use, which is only really useful for video/photo/database stuff, or if you just wanted a really fat ram disk ;) Most of the 64 bit uses will come later as programs get larger and need to address more bits.
     
  6. MacBandit macrumors 604

    MacBandit

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    Springfield, OR (Home of the Simpsons)
    #6
    Yeah but two double data rate 200MHz buses running at an equivalant of 400MHz = a total throuput of 800MHz. Remember the PPC970 doesn't have a 800MHz FSB it has a 400MHz out and a 400MHz input that are supposed to be able to work simultaneously thus the figure of 800MHz. To achieve the full capablilities of the FSB on the PPC970 you need two 200MHz DDR system buses.
     
  7. zuggerat thread starter macrumors regular

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  8. Wyrm macrumors 6502

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    Toekeeyoe, Japan
    #8
    AFAIK the 970 actually has a scaled FSB or a locked multiplier of 2x.

    So a Powerbook 970 at 1Ghz would use a FSB of 500Mhz, at 1.8Ghz a FSB of 900Mhz, etc. These are DDR values.

    This must make a support chip a little more complicated as it must asynchronously drive the IO bus - but then there is a rumour that Hypertransport will be used and these can have an asynchronous interface.

    Re: 64 bit computing
    It will probably make little difference in the short run unless you do lots of 64 bit math and don't use AltiVec, as the advantages of 64 bit computing is pretty much lost on a laptop. The thought of having more than 4GB of Ram on a laptop is really cool, but I guess we have to wait for bigger memory modules.

    The real advantage comes from the fact that the 970 has a future, or IBM has a future/real interest with PowerPC chips for something more than embedded applications. Improvements to the architecture (hence the "bus speed"x3 response), rather than pure Mhz speed, will make more of a difference.

    -Wyrm
     
  9. MisterMe macrumors G4

    MisterMe

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    USA
    #9
    Ever heard of virtual memory?
     
  10. Wyrm macrumors 6502

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    Toekeeyoe, Japan
    #10
    Yes, but since it is virtual (ie not real), and disk based, at several orders of magnitude slower than DRAM, having potentially gobs of virutal memory is not going to do anything for you, except make you pull out your hair.

    :D

    -Wyrm
     
  11. MisterMe macrumors G4

    MisterMe

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    USA
    #11
    To design is to choose. There may be many higher priorities in computer design and engineering than adding RAM to a machine with 512 MB or more already. A 64-bit processor's ability to address more than 4 GB of memory is a benefit, whether the memory is real or virtual. For now and for the forseeable future, however, virtual memory will remain much less expensive than RAM.
     
  12. whooleytoo macrumors 603

    whooleytoo

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    Aug 2, 2002
    Location:
    Cork, Ireland.
    #12
    I think the FSB is half the clock rate, so 1.8 GHz 970 has an effective 900MHz 64bit bus; which is actually two 32bit buses, both clocked at 450MHz double data rate. The 900 figure comes from the fact that they're DDR, not from there being two buses. You can't add frequency like that any more than you can call a dual 1.4GHz Mac a 2.8GHz machine.

    I think the 800MHz figure is the 'net' figure minus overhead (seems to be about 11%) ; just as the 6.4G effective data bandwidth is about 11% less than the total bandwidth of 7.2G.

    "I think" :)

    Mike.

    Edit: oops, fixed a typo..
     

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