multiprocessing

Posted:
in Current Mac Hardware edited January 2014
I'm just wondering what the deal is with the G3 and multiprocessing, everyone says it doesn't work but what's this?

<a href="http://www.everymac.com/upgrade_cards/totalimpact/totalpower_g3/totalpower_g3_400.html"; target="_blank">G3 card</a>

<a href="http://www.totalimpact.com/G3_MP.html"; target="_blank">here too</a>



Thanks.

Comments

  • Reply 1 of 5
    drboardrboar Posts: 477member
    Different CPUs has diffrent level of intrinsic support for working in multiples. IBM uses the very old 604E cpu in their RS 6000 servers they are not using G3s.



    Having PCI slots crammed full with CPUs to generate a redering farm in very specific applications does not equal having a ordinary multi CPU computer.



    If you take a look at the Sonnettech G3 upgrade of the 7200 and compare that to the G3 upgrades in the 7500 you will find that the 7200 were the G3 is ina PCI slot is way slower than the 7500 were the upgrade is in the CPU slot. This result suggest that having not one but even four G3 in a PCI card is only useful were there is a lot of CPU number crunching and not much traffic on the bus.



    If dual G3 would have been a viable alternative I am sure that the accelerator manufactures would have made them. A dual 800 MHz G3 for 500 dollars would been nice in a B&W G3 for example. Apple has marketing reasons to push the G4 but for the other ones any CPU that they can sell with a profit is good.



    I am sure almost any CPU can be made to rund in a dual setup., the question is rather if it is useful? If you have to have a vast array of support chips or goofy technical solutions to overcome the problems with CPUs not designed for SMP it is a waste of time and effort. The fact that IBM stayed with the 350 MHz 604E at a time when they had 700 MHz G3 as well suggests as much as they have proven track record about knowing something about multi CPU computers



    Waiting for the bright future of the 970 <img src="graemlins/cancer.gif" border="0" alt="[cancer]" />



    [ 02-26-2003: Message edited by: DrBoar ]</p>
  • Reply 2 of 5
    hmurchisonhmurchison Posts: 12,125member
    [quote]Originally posted by Galen:

    <strong>I'm just wondering what the deal is with the G3 and multiprocessing, everyone says it doesn't work but what's this?

    <a href="http://www.everymac.com/upgrade_cards/totalimpact/totalpower_g3/totalpower_g3_400.html"; target="_blank">G3 card</a>

    <a href="http://www.totalimpact.com/G3_MP.html"; target="_blank">here too</a>



    Thanks.</strong><hr></blockquote>





    BeOS ran on Dual G3 133Mhz BeBoxes. Don't let anyone tell you it can be done. The problem with the G3 doesn't support the necessary states of Cache Coherency. MERSI



    Mutual

    Exclusive

    Reserved

    Shared

    Invalid



    Without all support the OS cannot efficiently manage the caches of each Proc leading to efficiency problems.



    The G4 added full support hence it's use in Duallies.
  • Reply 3 of 5
    thttht Posts: 2,797member
    The PPC 750 (and PPC 603) did not have support for shared cache coherency, the "S" protocol. Which effectively meant that the PPC 750 could not have backside caches in SMP configurations. Essentially, one processor in a PPC 750 SMP config could not access data in another processor's cache. That piece of data would have to be written to main memory, then the other processor could read it. This causes quite a bit of bus contention and causes the system to be slower. A 750 with backside cache probably has the same performance, less in some circumstances, as a dual 750 w/o backside cache.



    The shared cache coherency protocol in the G4 allows processors to directly read another processor's cache without touching main memory. Less bus contention, therefore a more viable SMP system.
  • Reply 4 of 5
    be ran on dual 603e's, not g3's. the g3 was what killed be os on the mac platform, that and the g3 never ran at 133, it started at 233 mhz
  • Reply 5 of 5
    [quote]Originally posted by ThunderPoit:

    <strong>be ran on dual 603e's, not g3's. the g3 was what killed be os on the mac platform, that and the g3 never ran at 133, it started at 233 mhz</strong><hr></blockquote>



    Yes indeed Thunderpoint my error. My Gawd it's been a while since we were using 603e hasn't it?
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