True memory limits of systems

Discussion in 'Apple' started by JF Mezei, Mar 3, 2014.

  1. JF Mezei

    JF Mezei Guest

    Crucial tells me the max for a Mac Pro 2009 is 16 gigs, 4 * 4gb.

    I tried to order from Crucial however, they no longer offer shipping to
    Canada (they insist on UPS which is a deal breaker and that is before I
    even consider the $20 shipping cost).

    So I went to other on line stores who suggested 8gb and 16gb sticks for
    the 2009 Mac Pro.

    Apple's tech specs mention 16 gig max with 4 slots filled with either 1,
    2 or 4gb DIMMs. But those date from the time the system was produced, so
    if 8gig sticks were introduced later, the tech specs don't mention them.

    However, for the 2010 model, it mentions 8gb DIMMs which brings the
    limit to 32gigs for a single processor system.

    Is Crucial the authoritative source of the true memory limits on Macs ?
    Or have there been instances where they just took Apple's specs and
    didn't bother updating them ?

    I am currently at 12 gigs, and based on Crucial I could get an extra 4
    gig stick and go to 16. But if I find out that 8 big sticks are
    permitted, I might get 2 and then use the 4gb sticks to whatever limit.
    JF Mezei, Mar 3, 2014
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  2. JF Mezei

    JF Mezei Guest

    A bit more info:

    System Memory Interface
    — Memory controller integrated in
    processor package
    — 3 channels
    — 2 DIMMs/channel supported (6 total)
    — 24 GB maximum memory supported
    — Support unbuffered DIMMs only
    — Single Rank and Dual Rank DIMMs
    — DDR3 speeds of 800/1066 MHz
    — 512Mb, 1Gb, 2Gb,
    Technologies/Densities supported

    Would the 24 GB refer to 8gigs for each of the 3 channels ? Is it
    possible that Apple only implemented 2 channels on the MacPro 2009 ?

    Since 24 gigs is not an addressing path width limit (adding an extra bit
    to a 16GN system makes it support 32GB), where does the 24 GB limit come
    from ?

    Or is it a fair bet that my Pac Pro really has a 24 gig memory limit ?

    or is the only way to test this to buy 2 8 GB sticks, and then add 2
    extra 4 GB sticks to bring it to 24 and see what the system says when it
    boots ? Is it fair to state that if the system recognizes 24 gigs in the
    System Profiler that it will make safe use of the memory above 16 gigs ?
    JF Mezei, Mar 3, 2014
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  3. JF Mezei

    Lewis Guest

    The actual max for the 2009 quad core is 48GB. The 8 core can take
    128GB. (16GBx3 for the quad core).
    No. MacTracker is. OWC is also usually reliable.
    Lewis, Mar 3, 2014
  4. JF Mezei

    Your Name Guest

    The RAM limits are due to various things, including hardware and
    software limitations.

    Sometimes Apple's official RAM limits are due to the chips available at
    the time, but then later newer, higher capacity chips are *sometimes*
    released which are compatible and can be plugged in and used perfectly
    well. Personally though, I'd just trust Crucial rather than waste money
    on chips you find won't work.

    My beige PowerMac is works fine with just 288MB of RAM. :)
    Your Name, Mar 3, 2014
  5. JF Mezei

    JF Mezei Guest

    Thanks. Interesting that the app lists 48GB as limit, when the Intel
    document on the Xeon 3500 lists 24GB as limit. But this means it is
    very good odds of it being at least 24 GB, and not the 16 Apple claims.

    Note that the Intel document mentions only 512Mb, 1GB and 2GB modules
    supported. Obviously, bigger modules work since Apple made it work with
    4GB modules right off the bat.

    The intel doc says 3 channels, each supporting two DIMMs (6 max). The
    MacPro 2009 has only 4. Does it use only 2 channels ?
    JF Mezei, Mar 3, 2014
  6. It's a little more complicated than CPU specs.

    The channels is the concurrency of access. Not all of the channels need
    to be for main RAM. Some could be used for I/O or graphics.

    A CPU's memory limit doesn't need to be the same as a system's memory
    limit. 24GB is how much RAM the Xenon 3500 internal MMU can map at
    once. When there's an external memory controller, the operating system
    can use virtual memory page faults to access limitless additional RAM.

    From what I've Googled, the memory limit mostly depends on the OS
    Kevin McMurtrie, Mar 4, 2014
  7. JF Mezei

    JF Mezei Guest

    Doesn't Nehalem and beyond use an integrated memory controller in the
    CPU chip ? If so, wouldn't the specs for the Xeon 3500 be the true limit ?

    Found different specs page:

    the W3530 (2010 MacPro quad core): 36 bit address, Max memory 24 GB

    Apple quotes the Mac Pro 2010 as 32 GB max.

    On those pages, I can't find the "3500", but the "3520" has the same 24
    GB limit, 36 bit addressing.

    So it is pretty obvious that the CPU limits as listed by Intel are not
    "hard" limits since Apple was able to build the 2010 MacP[ro with 32 gig
    limit that is above the Intel specs of 24 GB.
    JF Mezei, Mar 4, 2014
  8. JF Mezei

    Savageduck Guest

    Here is what OWC has to offer. i am not sure of their Canadian shipping
    < >
    Savageduck, Mar 4, 2014
  9. JF Mezei

    JF Mezei Guest

    Thanks, This is interesting and seems to confirm that 8GB modules would
    be supported. I guess I need to do some shopping to see about pricing.
    (I might buy 2 8GB, to make my Pro 2*8GB+2*4GB, and put the extra 4GB
    into my Xserve.
    JF Mezei, Mar 5, 2014
  10. JF Mezei

    Alan Browne Guest

    Really? I bought memory from them in Oct. $10 by USPS. Took about 1 week.

    There was a "tax and fees" estimate of $24.60. Was never collected by
    the post office here.
    Try OWC too.
    Alan Browne, Mar 5, 2014
  11. JF Mezei

    Alan Browne Guest Shot 2014-03-04 at 19.48.40.jpg

    Says a Quad Core 2009 Mac Pro is good to 48 GB ("Actual") v. 16 GB
    Alan Browne, Mar 5, 2014
  12. JF Mezei

    JF Mezei Guest

    Got an email back from Crucial stating that USPS should work and that I
    should try on a different browser or zap all my cookies.

    Interesting how the 4GB sticks are all ECC Ubbuffered, but when you get
    into 8GB sticks, most are regustered without ECC. So gotta be careful
    choosing them.
    JF Mezei, Mar 5, 2014
  13. JF Mezei

    Lewis Guest

    16GB modules are supported. Up to 3 of them, for a 48GB maximum. As I said.

    The 8 core model can take 128GB.
    Lewis, Mar 5, 2014
  14. JF Mezei

    Alan Browne Guest

    Crucial do a good job stating which machines need which spec memory. OWC
    Alan Browne, Mar 7, 2014
  15. JF Mezei

    JF Mezei Guest

    In the case of the 2009 MacPro, Crucial says 16GB, OWC says 48GB.
    JF Mezei, Mar 7, 2014
  16. JF Mezei

    Alan Browne Guest

    I'm stunned! It's in Crucial's best interest to state the higher
    number, after all.

    Go with the larger figure. Esp. if confirmed by MacTracker.
    Alan Browne, Mar 7, 2014
  17. JF Mezei

    Lewis Guest

    The memory spec is not the same as the maximum RAM allowed. Crucial
    tends to stick with what Apple says. OWC lists the real maximum, as does
    Lewis, Mar 7, 2014
  18. JF Mezei

    JF Mezei Guest

    Ah, OK. I was under the impression that Crucial would test the true
    limits of systems. If they stick to limits from Apple, it explains the
    JF Mezei, Mar 7, 2014
  19. JF Mezei

    Barry OGrady Guest

    Sounds like a numbers game for boasting rights since any more
    than say 4 GB will make no noticeable difference.

    I currently only have 1 GB in my Intel Xserve and it gets a
    Geekbench 2 rating of 10555.
    Barry OGrady, Mar 9, 2014
  20. JF Mezei

    Barry OGrady Guest

    Have you tried Everymac?
    Barry OGrady, Mar 9, 2014
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