G5 Quad RAM Limit

Discussion in 'PowerPC Macs' started by NigeW, Feb 28, 2012.

  1. NigeW macrumors newbie

    Joined:
    Feb 7, 2012
    Location:
    Gloucester UK
    #1
    Hi. According to the build sticker on my G5 it shipped with 2 Gb of RAM. It still has 2Gb so I assume the original DIMMs are still fitted. The question is why are they clocked at 444MHz (according to the system profiler on ASD)when the motherboard goes up to 555MHz? Were Apple just saving a few pennies? This leads me on to my next question. I understand that the DIMM slots only support a maximum of 2GB but has anyone on here tried fitting 4Gb DIMMs? (As seen here:http://www.amazon.co.uk/Komputerbay...IE/ref=sr_1_48?ie=UTF8&qid=1330455843&sr=8-48). Thanks. Nige
     
  2. tayloralmond macrumors 6502

    Joined:
    Mar 26, 2009
    Location:
    Michigan, USA
    #3
    I recall a long debate thread on this topic. From what I remember, the G5 Quad is "technically" able to accept 32GB's of RAM, but nobody was able to confirm if OS X would actually utilize it properly or not because most people don't feel like spending hundreds of dollars just to find out.

    EDIT: By "technically," I mean it showed up as 32GB's of RAM in system profiler.

    EDIT (again): Also, in regards to your RAM question, my RAM shows up as PC2-4200-444 and I'm certainly not at the stock configuration with mine.
     
  3. NigeW thread starter macrumors newbie

    Joined:
    Feb 7, 2012
    Location:
    Gloucester UK
    #4
    Hi and thanks for that, but I had already seen it. I suspect 4Gb DIMMs weren't available back then. Wikipedia has this to say about the addressable limits of the processor: the PowerPC 970 processor is capable of addressing 4 terabytes of physical memory and 16 exabytes of virtual memory. I am not a computer whizz but would there be a 2Gb limit per DIMM in the BIOS?
     
  4. Xandros macrumors regular

    Joined:
    Sep 19, 2010
    #5
    If I remember correctly single slots can take 4gb modules, it isn't limited to 2gb per DIMM, but as someone else said it appears no one ever bothered to spend the cash on the modules to see if the memory controller actually recognises more than 16gb in total.
     
  5. thorns macrumors member

    Joined:
    Sep 27, 2011
    #6
    I believe it's a restriction of the chipset, but I'm not sure.

    Btw, the 444 digits appearing in system profiler are the timings for the RAM cycles and not the MHz speed of the RAM (thats 533, which is indicated by PC4200 with 4,2GB/sec being the theoretical max bandwith)
     
  6. G5 Mac Daddy macrumors member

    Joined:
    Feb 25, 2012
    #7
    32 GB of ram.... Thats hawt rite there... LOL!
     
  7. NigeW thread starter macrumors newbie

    Joined:
    Feb 7, 2012
    Location:
    Gloucester UK
    #8
    Thanks for all the replies. I never intimated that I want 32 Gb of RAM-these 4GB DIMMs are £35 a pop whereas 2Gb DIMMS are £17 so the smaller DIMMs are cheaper. I was just wondering if it was possible. The fact is that these older technology DIMMs are much more expensive than the newer DDR3 stuff-I've seen 8Gb (2X 4 Gb DIMMs) for the same price. I'm tired and "emotional" but will make a new post of exactly why I bought my Quad, the travails I've had with it and where I see it going in the future. Cheers. Nige
     
  8. G5 Mac Daddy macrumors member

    Joined:
    Feb 25, 2012
    #9
    I would have ram envy even with 16 gb of ram...
     
  9. Xandros macrumors regular

    Joined:
    Sep 19, 2010
    #10
    Yea, the thing is DDR2 is only ever going to go up in price now it has essentially started to become obsolete. It depends really on how you ever intend to use your Mac but, regardless, if you never intend on even going up to 16GB then just get 2GB DIMMs to Apple's specification, that way you can't go wrong on any count can you?

    Larger modules like 4GB single modules were only ever intended for specific scenarios anyway like servers, or for people with large amounts of dosh to blow, and the faster the memory becomes (such as DDR3) the more feasible larger module sizes become at lower prices. Apple's specs for your Mac may well state it as only holding upto 16GB RAM but they could either be directly referencing that they've built the memory controller to not recognise anything beyond that amount, or, they're just referencing the fact your average end-user wasn't ever likely to use modules larger than 2GB in size in any one slot.

    I don't think anyone has ever tried to put more than 16GB in their G5 Quad, and if they have they haven't bothered to advertise the fact for some reason, so it would seem no one could answer your question reliably. Besides, 16GB is a huge amount of RAM even by today's standards, and it's highly unlikely you'd need even half of that in any given situation you may be going to use your Mac for, so in reality it'd just be easier and more cost effective for you to adhere to Apple's specifications and buy PC2-4200 2GB modules.
     

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