Early 2008 Mac Pro: Wanting to upgrade RAM : (6x1gb) vs...?

Discussion in 'Mac Pro' started by svalle, Apr 13, 2012.

  1. svalle macrumors newbie

    Oct 14, 2011
    I have an early 2008 Mac Pro 2.8ghz 8-core. Upgraded to OSX Lion. 6gb of 667mhz ram in 1gb modules (I bought this computer about four years ago from ebay...and as I research, I wish they had installed 800mhz ram modules).

    I want to upgrade the ram but am trying to see what I should do with all these 667mhz pieces when I could have 800mhz.

    Should I buy (2x2gb) 800mhz and use 4gb operating at the higher speed instead of 6gb at the lower speed?

    Or should I buy (2x2gb) 667mhz and fill all my slots so that I have 10gb of ram?

    Thoughts and responses will be appreciated! :))
  2. flatfoot, Apr 13, 2012
    Last edited: Apr 14, 2012

    flatfoot macrumors 65816

    Aug 11, 2009
    Given the fact that those FB-DIMMs are rather expensive, I'd rather go with more RAM than faster modules. 800MHz vs. 667MHz is not that much of a performance difference, depending on what you use your Mac Pro for, of course.

    What you could do, however, is add a few 800MHz modules, which will down-clock to 667MHz automatically. This would give you the possibility to replace the 667MHz modules and get a few more 800MHz ones later.

    Of course, this only makes sense if the 800MHz modules can be had for the same amount of money as the 667MHz ones.
  3. svalle thread starter macrumors newbie

    Oct 14, 2011
  4. flatfoot macrumors 65816

    Aug 11, 2009
  5. gpzjock macrumors 6502a

    May 4, 2009
    If you have the money I'd invest in this:

    8 GB of 800mhz RAM is just under $200 http://www.memoryamerica.com/2fk225672800at.html
    Your memory should perform about 20% faster for this investment.
    Using 2 GB sticks allows you to expand further with the other 4 slots later if you wish.
    I would sell on the 667mhz on ebay or the like.
    I use those 800mhz modules and they are very good, they also come with a lifetime warranty.
  6. Greg M macrumors 6502

    Jul 13, 2008
    I believe that this thread has answered my question but I'd like to clarify if I can.

    A 2008 MP uses PC6400 ram but I can use PC5300 in it? Will there be any problems?

    I ask because I've got some 5300 ram that I'd like to use in my 2.8 8 core MP because I believe that more slower ram is more beneficial than less faster ram.
  7. flatfoot macrumors 65816

    Aug 11, 2009
    If you mix PC6400 and PC5300 RAM, the 800Mhz modules will be clocked down to 667MHz but work.
    I, too, think that more slower RAM is better than less faster RAM.
  8. Greg M macrumors 6502

    Jul 13, 2008
    This part I understand. The part that I'm not understanding is that the 2008 MP "requires" a minimum of 800Mhz RAM. If you could answer these questions it would help me understand that part. I've built plenty of PC systems in the past but never developed a complete understanding of the inner workings of the Processor, RAM and the bridges. I always just followed the stated minimum requirements for the RAM.

    When you put 667Mhz RAM in it the 2008 800Mhz MP will lower the bus speed to 667Mhz in order to match the slowest RAM?
    Does that cause any problems with any other part of the system?
    Will it slow down other parts of the system?
  9. gpzjock macrumors 6502a

    May 4, 2009
  10. Greg M macrumors 6502

    Jul 13, 2008
    I'm selling my 2 original MP that have 14gb of RAM between them. I can sell them with 2gb each and take the extra 10gb for my "new" 2008 MP which already has 10gb in it for a total of 20gb. Money is tight so if the slower ram doesn't present any problems in the 2008 MP then it will be very helpful. The computer is going to be used for Premium Pro, After Affects and Photoshop.
  11. gpzjock macrumors 6502a

    May 4, 2009
    Try it and see what the difference is.

    The only close comparison I can find in Geekbench for 800 vs 667 are these:
    Ignoring the CPU testing, the Memory and Stream numbers are quite different in the 800 Mhz's favour.
    The only way to really know is test it yourself.
  12. Greg M macrumors 6502

    Jul 13, 2008
    Thanks for the link. I wouldn't even think of putting slower ram in if I was buying the ram. I'm only considering the slower ram because I already have it and 10gb of faster ram isn't as good as 20gb of slower ram since the programs that I'm using will use the extra ram.

    I don't want to assume. No one has come out and said that the 2008 3.1 Mac Pro which requires 800Mhz ram will run without problems using 667Mhz ram. I understand that it will run a little slower but will it run without errors (due to the slower ram)?

    I've searched on the web and haven't been able to find the answer.

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