RAM Upgrade in Mac Pro not working so well...

Discussion in 'Mac Basics and Help' started by Sam1487, Jan 18, 2009.

  1. Sam1487 macrumors member


    Jan 18, 2009
    Between Nottingham & Derby, UK
    Hi ladies and gents, first post here.

    So I finally got around to buying some more RAM for my Mac Pro and sadly, I'm having problems with it.

    I used the Crucial scanner for macs, and checked all over their website and it kept telling me that my December 2006 Mac Pro will support up to 32Gb of RAM, in which case I bought two sticks of 4GB of RAM seeing as that would work (it's the maximum allowed in each stick according to Apple and 8 (slots) x 4 (gigs) = 32GB.

    However, when I came to install it, the sticks did not like being on separate cards (which is suggested by almost everyone), I tried them with the existing RAM, then again in slot 1 with the old RAM positioned below it, and finally without the existing RAM and just the new RAM. For some reason, the Mac would not recognise the new sticks, giving me only 4 gigs of RAM (when I tried it with the new sticks in the top slot and the old RAM below it it gave my 4.5 gigs).

    I should mention at this point that I currently have 2 gigs of RAM in my Mac split across the two cards with four sticks of 512MB.

    I currently have 1 card with 9 gigs on it, and the other card with 1 gig on it, and it does register that as 10GB.

    But I am starting to notice a problem: when I wake my Mac up from sleep the mouse has frozen, I cannot do any keyboard commands, and nothing else happens on screen. It appears the whole Mac has frozen save for the noise coming out from the Mac like it is working away at something.

    On a few quick blasts around the internet I have discovered a worrying notion that my model of Mac Pro can only handle 16GB of RAM max, meaning that each RAM stick should only be a maximum of 2GB each. I thought I had heard this long ago but with everywhere seemingly telling me that it could handle 32GB I assumed the 16GB limitation was from the software at the time (Tiger) and the new OS (Leopard) allowed it handle double the RAM of it's older brother.

    I was wondering if anyone else could shed some light on this as to what the problem could be. I'm not worried about my money being wasted as Crucial offer a "wrong RAM, full refund policy", although I'll still get the RAM just in 2GB stick form.

    So, any help, advice, experiences floating around out there?

    (Apologies if this is in the wrong place :))
  2. BlueRevolution macrumors 603


    Jul 26, 2004
    Montreal, QC
    Yes, your computer "only" supports 16 GB of memory.


    Crucial mis-identified the memory for my iBook as well, saying I needed PC133 rather than PC100.
  3. Sam1487 thread starter macrumors member


    Jan 18, 2009
    Between Nottingham & Derby, UK
    Luckily they have that guaranteed money back if their scanner tells you wrong. I sent the RAM back and got myself 4 sticks of 2Gb and they work like a charm.

    Thanks for the reply and the help :)

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