RAM differences

Discussion in 'Buying Tips and Advice' started by irishgrizzly, Jan 13, 2008.

  1. irishgrizzly macrumors 65816

    irishgrizzly

    Joined:
    May 15, 2006
    #1
    Was curious about the different RAM types. I know very little about the technical side of it, but in layman's terms I wonder what difference newer RAM makes to the better running of a computer? The attached pics show 1 gig sticks of the same amount of RAM from different generations of mac (PowerMac and Mac Pro) is the newer RAM functionally any better?
     

    Attached Files:

  2. nslyax macrumors regular

    Joined:
    Jul 29, 2002
    Location:
    Holland, MI
    #2
    For the two you listed, for example, one is PC-3200 and the other PC-5300. The PC-3200 operates at 400MHz, where the newer PC-5300 operates at 667MHz. Obviously, faster RAM lets the processor read and write to it faster, and thus the system as a whole operates faster.
     
  3. irishgrizzly thread starter macrumors 65816

    irishgrizzly

    Joined:
    May 15, 2006
    #3
    So let's say (making this up for sake of discussion) 6 gigs in a G5 may be inferior in RAM heavy tasks then 4 gigs in a Mac Pro?
     
  4. nslyax macrumors regular

    Joined:
    Jul 29, 2002
    Location:
    Holland, MI
    #4
    That is more complicated. Kind of like 3GB in a MacBook versus 2GB that is interleaved. In some instances and programs more RAM is better, in others interleaving gives you a benefit.

    Maybe somebody else will answer? Wikipedia might have some answers, though they can be written a little too technical sometimes.
     
  5. DrRock macrumors regular

    Joined:
    Jun 18, 2005
    #5
    Similar question

    Sorry to hijack the thread, but I didn't want to start another if my question could be answered here.

    I have a G5 2x2.3 GHz, currently with 512mbs of DDR SDRAM (256 ea. in two slots), and I want to load up to make applications like FCP, Photoshop, etc. work faster. What's the limit of RAM I can put in my machine, and is it beneficial to use bigger sticks in each slot, or if there is a limit, should I spread them out?

    Also, I bought 2 1GB sticks at Best Buy for about $30/ea. (Kingston DDR-2 PC2-5300 533MHz/667MHz). Is this the right RAM for my machine, and if not, what should I use? And, is it a good price? It seems like it was decent. Thanks!

    *edit:
    I checked the Kingston site, and it says I can go up to 8GB, and to use the 3200 sticks. Does anyone know if there's a problem with using the 5300 sticks in my machine? Also, their site lists the 1 gig sticks at $99/ea. so I guess if it works in my system, it was a good deal.
     
  6. CanadaRAM macrumors G5

    CanadaRAM

    Joined:
    Oct 11, 2004
    Location:
    On the Left Coast - Victoria BC Canada
    #6
    DDR (PC3200) and DDR2 RAM (PC2-4200, PC2-5300) are different electrically and physically - they are not compatible with each other.

    You have to specify whether you have a Dual-Processor 2.3 GHz G5 (PCI-X bus, DDR PC3200 RAM)

    or a Dual-core 2.3 GHz G5 (PCI-e bus, DDR2-4200 RAM) which was built after Oct. 2005

    You cannot 'improve' the memory speed on either machine, you are stuck with what Apple designed it for.

    That said, you need a MINIMUM of 2 Gb for any kind of professional software to perform to its potential, and 4 Gb would not be out of place for graphics, video or audio work.

    I advise you to stick with a reputable memory dealer who knows Macs and can guarantee compatibility with your specific model Mac. BestBuy and other discounters will happily sell you the wrong thing if you order it, and it's your time and money wasted to send it back.

    To the original question:
    The speed of RAM performance is determined by the memory bus speed (which is set by the motherboard, the higher the better) and by the latency of the RAM (Lower the better, limited by the capability of the RAM module, and the capability of the motherboard to run the RAM at lower latency).

    Whether 2 types of RAM are can be compared directly is a little tricky. Yes, the DDR RAM is a 400 MHz module and the DDR2 RAM is a 667 Mhz. But the 400 MHz RAM runs at a CAS latency of 3, while the 667 MHz DDR2 RAM runs at CL 5, which cuts its speed advantage down a bit.

    The FB-DIMMs in a MacPro are another story entirely. The FB-DIMMs have an advanced memory controller chip on the DIMM, so they offload some of the management from the CPU, allowing for larger memory sizes, highly reliable Error Correcting, and easier motherboard design. The tradeoff is heat, and latency. FB-DIMMs run between CL 7 and CL 9 depending on which slot they are in on the riser. Slots 3 and 4 are slower than slots 1 and 2, because all requests are first sent to the lower slot, and then forwarded by the controller on the first FB-DIMM to the upper slot, which causes added latency.


    G5 Dual Processor = DDR 400 MHz @ CL3
    G5 Dual-core = DDR2 533 MHz @ CL5
    MacPro = DDR2 FB-DIMM 667 MHz ECC @ CL7
    MacPro Penryn = DDR2 FB-DIMM 800 MHz ECC @ CL7 (? possibly, we don't know the latency yet)

    When you get into comparing the speed effects of DIFFERENT sizes of different types of RAM, then all bets are off. On top of bus speed and latency, it depends on how much RAM, how many programs you are using, how big the data is, how well the programs and the OS exploit more RAM, etc. There is very little way to make any informed guesses with so many variables.
     
  7. DrRock macrumors regular

    Joined:
    Jun 18, 2005
    #7
    ^

    Ok, here's what it says in System Profiler:

    Machine Name: Power Mac G5
    Machine Model: PowerMac7,3
    CPU Type: PowerPC G5 (3.0)
    Number Of CPUs: 2
    CPU Speed: 2.3 GHz
    L2 Cache (per CPU): 512 KB
    Memory: 512 MB
    Bus Speed: 1.15 GHz
    Boot ROM Version: 5.2.4f1

    Ram slots 1&2 both list this:
    Size: 256 MB
    Type: DDR SDRAM
    Speed: PC3200U-30330
     
  8. DrRock macrumors regular

    Joined:
    Jun 18, 2005
    #8
    ^

    Thanks for the info, CanadaRAM. It helps a lot! So now that I know what to get, who knows the cheapest place to get it?
     
  9. DrRock macrumors regular

    Joined:
    Jun 18, 2005
    #9
    Additional question

    I want to max out my system with RAM (8GB), and Apple tech support suggested using the 1GB sticks, thereby filling each slot, which would give me the best performance overall.

    I am having a hard time finding the 1 GB sticks at a low price (at least low enough to justify buying 8 of them). I'm finding it to be $50 per stick & up. Amazon, however, has the 2GB sticks in a 2-pack for around $40 each. That would max me out for under $100.

    Does anyone know if using eight 1GB sticks vs. four 2GB sticks would be that big of a performance difference? And have they noticed any difference between that configuration, and only using half the slots? And if so, is is worth the money?
     
  10. nslyax macrumors regular

    Joined:
    Jul 29, 2002
    Location:
    Holland, MI
    #10
    Are you sure it is 2 sticks of 2GB each, and not 2 sticks of 1GB each?
     
  11. DrRock macrumors regular

    Joined:
    Jun 18, 2005
    #11
    ^

    Well, I looked back at it, and I either can't find the deal I saw, or I misread it. I did find what looks like a 2x1GB stick deal for $53 at memoryamerica.com Has anyone dealt with them? If so, any problems?
     

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