1 gb unmatched ram better than 512 matched?

Discussion in 'Mac Basics and Help' started by jkandell, Sep 19, 2005.

  1. jkandell macrumors member

    Joined:
    Sep 6, 2005
    Location:
    Tucson AZ
    #1
    My iMac comes with 512 mb ram. For financial reasons I can only afford 1 gb additional. Am I right to assume it's better to add 1 GB to the 512 (making 1.5 gb "unmatched") than to add another 512 mb (1 gb matched) just so it would match?
     
  2. paperinacup macrumors 6502

    Joined:
    Mar 30, 2005
    #3
    That computer doesn't support dual channel (I dont think) So yes I would go ahead and get the 1gb.
     
  3. jsw Moderator emeritus

    jsw

    Joined:
    Mar 16, 2004
    Location:
    Andover, MA
    #4
    I'd say that, in most cases, that is absolutely true... unmatched RAM is vastly faster than swapping to the hard disk.
     
  4. Sun Baked macrumors G5

    Sun Baked

    Joined:
    May 19, 2002
    #5
    All depends on the amount of memory you really need.

    If you don't use a whole lot, and won't get many pageouts with 1GB -- the matched pair would be best.

    If you need the space, 1.5 GB is a lot better -- even if you do take a slight penalty in speed by not having matched memory.

    Since RAM is a whole lot faster than the penalty incurred by resorting to VM and using the HD and a measly 50MB/s sustained -- compared to memory running at 3200MB/s.

    If you are incurring the VM penalty, it won't matter if you are running in single- or dual-channel mode -- it will be very slow.

    So more memory is usually better, than not enough.
     
  5. madmax_2069 macrumors 6502a

    madmax_2069

    Joined:
    Aug 17, 2005
    Location:
    Springfield Ohio
    #6
    yea more ram is better than vm yea so much faster than vm.what diffrent about the ram is it speed if im not mistaken (example) say like you had a pc 133 and a pc100 sdram and u mix them togeather the pc133 will now run as fast as the pc 100.but any things faster than the vm yea i wouldent care if the sticks wer mismatch if it works it works you will have more ram but it will be a tad slower cause the ram installed will be as fast as the slowest ram chip you got installed.but like every ons said it will still be a hell of alot faster than vm.
     
  6. yenko macrumors 6502a

    Joined:
    Aug 29, 2005
    Location:
    SouthWest-USA
    #7
    This is what Apple says. I'm assuming you have a G5 iMac? :eek:

    iMac G5: Benefit of using matching memory modules (RAM)
    If your iMac G5 has matching memory modules, which are known as "DIMMs," it will operate with a 128-bit data path. If the DIMMs aren't matched, then it uses a 64-bit data path. So why does this matter to you?
    64-bit vs. 128-bit bus
    A 128-bit data path allows greater throughput than a 64-bit data path, in the same way that a 4-lane highway allows more traffic than a 2-lane highway. This allows the computer to manipulate large files faster. With a 128-bit bus, you would see better performance from the iMac when you have multiple applications open at the same time. On the fun side, you would also see some enhanced gaming performance.

    "Composition" of your RAM
    Composition refers to size, speed and devices on the chips you're using. If you want a 128-bit data path, you need to match composition of the two DIMMs you use. For example, if you have a 256 MB DIMM with latency of PC3200 - 30330 and 8 devices, you'll want to install an additional 256 MB DIMM with the same characteristics.

    Whoa?!
    If that technical stuff sounds scary, don't worry. There's an easy way to make sure they match. Just buy your DIMMs at the same time as a matching pair, like socks.
     
  7. CanadaRAM macrumors G5

    CanadaRAM

    Joined:
    Oct 11, 2004
    Location:
    On the Left Coast - Victoria BC Canada
    #8
    It's not dual channel but the iMac G5 allows for 128-bit memory access if the RAM are "matched" as to their speed, size and composition (as noted above). This gives a theoretical gain of 0% to 30% in memory access speed under certain conditions. However, www.barefeats.com measured the real world difference in several applications and there conclusion was that on average there was zero difference.

    Whereas: an extra 512 Mb makes a measurable difference in machine performance when you use programs and data of more than 1 Gb in memory requirements.

    So: 2 x 512 matched may be marginally faster than 1 x 1 Gb, but 1.5 Gb unmatched trumps 1 Gb matched.

    It's not really similar to the PC133/PC100 comparison because the RAM has to be PC3200 (400 MHz) regardless, and also, any Mac that takes PC100 will NOT run faster with PC133 in it -- the memory buss speed is fixed in every Mac I know of.

    Thanks
    Trevor
    CanadaRAM.com
     
  8. madmax_2069 macrumors 6502a

    madmax_2069

    Joined:
    Aug 17, 2005
    Location:
    Springfield Ohio
    #9
    no what i was saying if the system did use the pc133 (witch i know it dont) to the fullest extent and you put a pc100 chip in it it will dumb down the pc133 chip to the same standerd as the pc100 chip or visa versa but that was just an example.i know he was talking about the size diffrence of the two chips making it a mismatch.when they are a match set is it like useing a raid hdd setup i cant remember witch raid setup uses each hdd to store diffrent parts of the same file to each hdd
     
  9. CanadaRAM macrumors G5

    CanadaRAM

    Joined:
    Oct 11, 2004
    Location:
    On the Left Coast - Victoria BC Canada
    #10
    In a Mac that used PC133 memory, putting in PC100 would make it crash... ;)
    A Mac that uses PC100 memory will not speed up to PC133.
    This may be true of selected PCs, bur not Macs.
     

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