seeking advice on buying a Mac Pro for a mathematician

Discussion in 'Mac Pro' started by beethovengirl, Jan 24, 2008.

  1. beethovengirl macrumors regular

    Joined:
    Jan 15, 2004
    #1
    Hi,

    My husband is a math professor and is considering buying a mac pro on his grant, so while it's not really our money that is being spent, it doesn't mean that there are no price considerations.

    First, he is deciding between one or two 2.8 GHz processors. He mostly uses his computer for running PARI [a number theory program described here: http://pari.math.u-bordeaux.fr/ ] in Terminal, Safari, and Mathematica. Which do you think makes more sense?

    He already owns a Dell ultrasharp 2000FP 20" flat panel LCD. He was going to get an Apple Cinema Display if they'd been updated, but they haven't been, so we're thinking of waiting until they're updated, as he'd like to have built-in iSight. What are the disadvantages of the Dell display compared to buying an ACD right now? I called the Apple Store to see if the Dell was even compatible with the Mac Pro, and she told me that if we bought a DVI-DVI adapter, that would work. I asked, "Wouldn't that just be a DVI cable?" She said no. Then I asked if Apple sold this, and she pointed me to the mini-DVI/DVI adapter. I asked her if the Mac Pro had a mini-DVI port, and she wasn't sure. So, I'm not sure how we can get reliable advice on this matter from Apple, as I can't seem to find a way to email the Apple Store for questions.

    Also, if he gets a 2nd hard drive, can that be used for Time Machine back-ups, or is he better off just getting an external hard drive?

    Finally, I'm really confused about the RAM issue. I read that thread below about how adding more RAM that is not matched could be worse than just the 2 GB the Mac Pro ships with. I'm not clear on what it means for RAM to be matched or not. I'm starting to think he may be better off just buying Apple RAM? :(

    I'd appreciate any advice you may have. thank you :)
     
  2. gazfocus macrumors 68000

    gazfocus

    Joined:
    Jan 3, 2008
    Location:
    Liverpool, UK
    #2
    Hi. Firstly, I am in the same position as your husband. I cannot decide between the single or dual CPU model.

    The Mac Pro's come with a standard DVI connector so as long as your Dell monitor has a DVI port, you'll be fine using it with the Mac Pro. If it only has a VGA port, you can get a VGA to DVI adaptor from Apple.

    An additional internal drive can be used for Time Machine, and will actually work quicker than an external drive, although some people say that the external drives are a safer option (in the case of a complete system failure, etc). The other option is to get an Apple Time Capsule. If you have more than one Mac with Leapard, Time Capsule can back up multiple machines to one drive.

    As for RAM, whatever you do, don't buy the additional RAM from Apple. Buy it from Crucial, OWC, or Newegg.

    Basically, companies sell RAM in 'kits' so you don't really need to worry about them matching. The trick is, to fill 4 of the RAM slots for maximum performance. Therefore, if you are buying 8GB RAM for the Mac Pro, buy a kit that is 4 x 2GB sticks rather than 2 x 4GB sticks.

    I hope this helps a little.
     
  3. kps macrumors regular

    Joined:
    Jan 10, 2008
    Location:
    kw.on.ca
    #3
    It's not obvious whether PARI can use multiple cores. Mathematica can, but whether that's useful depends on what you're doing with it.

    Keep the Dell monitor for now. The video cards have standard DVI connectors; you don't need a new cable.

    Edit:
    The Mac Pro comes with one.


    Yes, an internal drive can be used for Time Machine. They are easy to install; you don't need to buy it from Apple.

    They should be matched in size in sets of four. That is, if you have (say) 2x1G on one card and 2x2G on the other card, performance will be slightly worse than 4 of the same size.

    Get the base 2 x 1G from Apple. Then, what to do depends on how much total memory you want:

    4G -- add 2 x 1G; put the Apple 2 x 1G together on one card (ie move one of them) and the other 2 on the other.
    8G -- add 6 x 1G; put the Apple 2 x 1G on one card and fill the other slots.
    12G -- add 2 x 1G and 4 x 2G.
    16G -- add 8 x 2G; sell the Apple memory.
    20G -- add 2 x 1G and 4 x 4G.
    24G -- add 4 x 2G and 4 x 4G; sell the Apple memory.
    32G -- add 8 x 4G; sell the Apple memory.

    In the cases where you have four of one size and four of another, put the larger ones in the first (inner) two slots of each card, and the smaller in the last (outer) two slots.
     
  4. gazfocus macrumors 68000

    gazfocus

    Joined:
    Jan 3, 2008
    Location:
    Liverpool, UK
    #4

    This information is incorrect. If having 4GB, yes, I would suggest 4 x 1GB sticks. However, if you are having 8GB, you would be better with 4 x 2GB sticks (2 sticks in each riser board). You also wouldn't see a performance increase by keeping the 2GB Apple RAM as well as the 8GB 3rd Party.

    The 4 x 2GB scenario makes more sense, as it performs better than 8 x 1GB sticks, and it allows for easier upgrading in the future (You won't have to sell your 1GB sticks to upgrade, you just buy additional 2GB sticks).
     
  5. beethovengirl thread starter macrumors regular

    Joined:
    Jan 15, 2004
    #6
    Why does 4 x 2 GB perform better than 8 x 1 GB?

    Is there a website that explains this? I don't understand this stuff :/
     
  6. beethovengirl thread starter macrumors regular

    Joined:
    Jan 15, 2004
    #7
    Thanks, that's a cool graphic! Did you create it or is this a graphic from Apple or...?

    Why are some configurations in black?

    It says the opposite of what the OWC salesmen recommended for ordering 4 x 2 GB for a total of 10 GB. We're deciding between buying 6 x 1 GB (total = 8) and buying 4 x 2 GB, either leaving in the 2 x 1 built-in Apple RAM or removing/selling the Apple RAM since some people seem to say that 4 x 2 + 2 x 1 < 4 x 2.
     
  7. kps macrumors regular

    Joined:
    Jan 10, 2008
    Location:
    kw.on.ca
    #8
    Those are the better choices.

    BTW, that diagram is for last year's Mac Pro; the current one can take twice as much memory, but the principles are the same.

    Ignoring the special case where there are only two sticks in total (the base configuration), it is easier to think of it as 4 pairs rather than 8 slots -- two cards (top and bottom) and two positions on each card (inner and outer).

    The two sticks in each pair must be the same size and should be identical (same manufacturer, batch, etc).

    The machine will be faster if the corresponding upper and lower pairs are the same size. This lets it use both pairs simultaneously rather than separately. That is, top inner the same size as bottom inner, and top outer the same size as bottom outer.

    The two inner pairs are fractionally faster than the two outer pairs, and the machine will use them first. So put the largest, size-matched pairs on the inside, and the smaller or unmatched pairs on the outside.

    4 x 2G will give you more flexibility in adding more later if necessary. In that case, do keep the Apple 2x1G in the outer upper pair; it won't be quite as fast as if you added another 2x1G in the outer lower pair as well, but having memory is always better than not having it.
     
  8. gazfocus macrumors 68000

    gazfocus

    Joined:
    Jan 3, 2008
    Location:
    Liverpool, UK
    #9
    I think looking at it, it's more from an upgrade perspective. I did read somewhere about the performance being better being 2 x 4GB but I can't find where I read it.
     
  9. Mackilroy macrumors 68040

    Mackilroy

    Joined:
    Jun 29, 2006
    #10
    Actually, they can both take the same amount of memory, Apple just didn't initially tell everyone they could.

    I can easily confirm that Dell monitors work with a Mac Pro, I have a 20" 207WFP hooked up to mine. I'd go with another internal drive, as it would be faster and it's extremely simple to install a new internal one. And if he's running Pari and Mathematica… I'd go with two 2.8 GHz processors.

    Just my two cents. :)
     
  10. edesignuk Moderator emeritus

    edesignuk

    Joined:
    Mar 25, 2002
    Location:
    London, England
    #11
  11. CalfCanuck macrumors 6502a

    Joined:
    Nov 17, 2003
    #12
    While I agree with most of what you say, recommending the user to only use the 8 GB of RAM and leave out the stock 2 GB is not correct.

    Here's what barefeats (who's testing started the entire matched pairs dbate) has to say:

    -----

    "CAN I KEEP THE TWO FACTORY 1GB FB-DIMMs INSTALLED?
    Some of you ordered your Mac Pro with the basic two factory 1GB FB-DIMMs. You are asking if you order four 2GB FB-DIMMs if you can install them along with the factory memory (for a total of 6 FB-DIMMs or 10GB of RAM).

    I tested the 10GB scenario. I put four 2GB FB-DIMMs -- two on each riser in slots 1 and 2. Then I put the two 1GB FB-DIMMs in slots 3 and 4 on the top riser. With that config I get the same fast memory fill rates in Xbench as I did with just the four 2GB FB-DIMMs (two on each riser, slots 1+2). But I'm told by those who l know that the four matched FB-DIMMs will perform better when you get into a heavy duty multi-threaded app that uses a signficant amount of memory. Eight matched is even better.

    You wil note that the two 1GB factory FB-DIMMs come installed one on each riser. If you are going to keep them installed along with the four matched FB-DIMMs, you'll want to move them to the same riser. If you don't, for some reason, the Mac Pro won't see them and report just 8GB total.

    In summary, I installed the four 2GB FB-DIMMs in slots 1+2 on each riser. Then I put the two factory 1GB FB-DIMMs in slots 3+4 on the top riser. That reported 10GB and produced the same fill rates as the four or eight stick configs in our brief testing.

    Some of you just want to buy two 2GB FB-DIMMs to add to the two factory 1GB FB-DIMMs for a total of 6GB. That configuration will slow you down. Don't do it. Again, the BEST performance setup is eight matched FB-DIMMs. The second best is four matched FB-DIMMs."

    -----

    As he said, in "theory" using the stock 2GB slows you down, but he couldn't detect the slowdown in his tests. And even if this theoretical slowdown does occur, you have to balance the MASSIVE slowdown from caching to disk that would occur with less RAM if you left 2 GB of RAM out (assuming the program could access it) against a theoretical minor slowdown from the RAM.
     
  12. CV4 macrumors member

    Joined:
    Apr 7, 2007
    Location:
    Ontario, Canada
    #13
    Is it not still the same basic principle though?

    If not, my mistake.
     
  13. Eraserhead macrumors G4

    Eraserhead

    Joined:
    Nov 3, 2005
    Location:
    UK
    #14
    It is probably worth keeping the Apple RAM rather than selling it as the non-Apple RAM isn't covered by Apple's warranty, so if your computer goes wrong you'll need to test it with the Apple RAM in, unless its obviously not a RAM issue.
     

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