iMac memory....does it really matter?

Discussion in 'iMac' started by kerpow, Dec 7, 2006.

  1. kerpow macrumors 6502

    Joined:
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    London
    #1
    Does it really matter what memory you put in an Intel iMac? I have 2x 1gb HP DDR II - 400 MHz / PC2-3200 chips in a PC. I know some people are memory snobs and thats fine but on my budget I simply can't afford to buy a 2gb memory kit.
     
  2. swiftaw macrumors 603

    swiftaw

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    #2
    I believe it has to be PC-5300 DDR2 667Mhz 200pin
     
  3. OldSkoolNJ macrumors 6502

    OldSkoolNJ

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    #3
    With Memory you can not put in memory that is slower speed in most cases. YOu can put in afster speeds that is backwards compatible which will of course run at the speed of which the computer is designed to take. You can run any brand you would like as long as it is DDR2 PC2-5300 SO-DIMM (laptop size) memory or a memory that is backwards compatible. At this point there is only one memory out that is faster and backwards compatible and that costs more money so you are stuck with buying what works. CompUSA has PNY Optima memory on sale this week for 50% off that is perfect for the Intel Macs. It is PNY Optima 1GB DDR2 PC-5300 SO-Dimm which is normally $160 and there is a $50 instant rebate and then a $30 MIR.

    Kevin
     
  4. robbieduncan Moderator emeritus

    robbieduncan

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    #4
    Also note that the iMac takes "laptop" RAM, i.e. SO-DIMMs not standard full-size "desktop" ram.
     
  5. kerpow thread starter macrumors 6502

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    #5
    I know that is what Apple sell with an iMac and if you go to Crucial or somewhere like that and choose iMac it will recommend that memory as well. I have no doubt that that is the optimal *memory* to use.

    But in the real world you should be able to use any memory as long as its the right type. Any DDR2 memory should be ok. I do it with my servers at work all the time. I wouldn't suggest mixing memory types but if you use slightly slower memory than a motherboard is capable of using there should be no harm done.

    I just hoped that some RAM guru might bite.
     
  6. clevin macrumors G3

    clevin

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    Aug 6, 2006
    #6
    as long as u can physically put it in, then the only problem would be that you are running it overclocking, Im not sure if that would cause over heat or other problems.
    there shouldn't be any "backward compatibility" problem, since they are both DDR2, and have no architectural difference.
     
  7. kerpow thread starter macrumors 6502

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    #7
    Ah, didn't know that. That kind of puts a spanner in the works.
     
  8. rogersmj macrumors 68020

    rogersmj

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    #8
    This isn't rocket science. Yes, you have to use a certain minimum speed RAM, and that speed is what Apple sells it with. The bus speed between the processor and RAM is what determines the minimum speed your memory has to be; in the case of the current iMacs, it's 667 MHz. It's not a marketing gag; it's the nature of the architecture. I would not risk putting slower speed memory in there. At the very least, you risk burning out the memory chips. At worst, the failure of the memory modules could mess up your system in other ways.
     
  9. robbieduncan Moderator emeritus

    robbieduncan

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    #9
    As long as it will run at the correct speed. Apple machines will not run with slow RAM. The reason for this is that this would force the FSB speed down which the CPU will not accept. You can run faster RAM as this will downclock fine.

    Some PCs may accept slower RAM and a drop in FSB, Macs will not.
     
  10. Eraserhead macrumors G4

    Eraserhead

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    Nov 3, 2005
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    UK
    #10
    Slower memory wont stop your Mac running properly some people have had MBP's which came with 533Mhz RAM and it works fine, any PC-2 (DDR2) SODIMM will work in the iMac, but if it isn't 667Mhz or faster it will slow the computer down, obviously buying faster RAM is usually silly as it is more expensive.
     
  11. clevin macrumors G3

    clevin

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    Aug 6, 2006
    #11
    how does mac detect this? sounds interesting, any detail?
     
  12. robbieduncan Moderator emeritus

    robbieduncan

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    #12
    Every RAM module as it's timing info in a ROM chip that is accessible to the chipset. This states the acceptable speeds and timings for that module.
     
  13. kerpow thread starter macrumors 6502

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    #13
    Thank-you, someone who can actually confirm this for me.

    Memory does not have to be the same speed as the FSB. Our HP Proliant servers come with 400mhz memory and have a 800 mhz FSB.

    As you say, it will be slower but I'm willing to bet I'll get better performance out of 2gb 400mhz than 1gb 667mhz which is what it really boils down to.
     
  14. clevin macrumors G3

    clevin

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    Aug 6, 2006
    #14
    well, i have no problem with that, every pc have that too. I was asking that if a mac will try to fetch that info and prevent system from starting because of wrong speed info?
     
  15. robbieduncan Moderator emeritus

    robbieduncan

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    #15
    The 800Mhz is a marketing number! It's a 400Mhz bus transferring data twice per cycle.

    Modern Macs (say the Mac Pro) have quad-pumped buses. So they transfer data 4 times per clock.
     
  16. robbieduncan Moderator emeritus

    robbieduncan

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    #16
    I believe so, although others are reporting that their Macs have happily started with slower RAM.
     
  17. SimonTheSoundMa macrumors 6502a

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    #17
    Hence, DDR.
     
  18. hob macrumors 68020

    hob

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    Oct 4, 2003
    Location:
    London, UK
    #18
    So what's actually the best RAM to buy? I want to get another 1GB into my iMac Intel Core Duo. The one that crucial recommends (DDR2 PC2-5300) seems to go up and up in price all the time...
     

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